CASIO fx-991EX - Using SOLVE to solve an equation for x

[@ompabaletserametse8643]

Thank you Sir, you have saved me a lot of anguish. I found this video 1 day before my exam. God Bless.

[@scottcollins7513]

I am glad you found it helpful. Thanks for leaving a comment. Hope your exam went well.

[@ompabaletserametse8643]

@@scottcollins7513 Yes it went well ! I used the method in the video to solve an equation that required the use of iterations. Thanks again.

[@Arbiter902]

Thank you soooo much! I used to calculate everything manually in college now it will be much faster!

[@scottcollins7513]

Glad you found it helpful and that let me know. Even if you are an algebraic wizard, it can still be a time saver - and there are some situations where normal algebra is not enough.

[@Alana-nd4ih]

Thank you so much I appreciate it I kept on getting the error sign

[@GabriTell]

Do you know that feeling that you've been doing wrong all your life? OMG... I wish I had known that many years ago, but late is better than never... ✨

[@kaybhee6]

one of the bestest....Casio... pay this man to work for you

[@scottcollins7513]

Thanks, Kay Bhee! You rock.

[@youssefkharroubi3853]

bestest?

[@adibashahrim2344]

Thank u sir,🇧🇩 I've got exam tomorrow...This trick's gonna help a lot!!🥰

[@scottcollins7513]

Glad it helped out -- hope the exam goes great for you. Thanks for letting me know.

[@tunseducation2561]

I tried with the negative and it worked then why you didn't?

[@Tamuz95]

Is it possible to use this with a polynomial ? for example x^2-3x-10. I know you can solve this using Setup, A, 2 , 2. When I try it will only give me x=5, but how can i also make it give me x= -2

[@scottcollins7513]

This video (kzbin.info/www/bejne/nJSul418pNiUitE) shows you how to find the roots (solutions) to a quadratic equation which is what you are asking for.

[@scottcollins7513]

Sounds like you are in the right place -- you may just need to hit = key again to get x2 (2nd root).

[@Xiif45]

Thank you so much rlly helpes

[@mahrukhbangash9186]

Yeah bro thank uuuuuuu so much ....i watched a thousand vids but found nothing and after seeing this i was like shocked as well as ecstatic

[@scottcollins7513]

Always happy to hear when the videos were helpful. Thanks for letting me know, Mahrukh.

[@mahrukhbangash9186]

@@scottcollins7513 thank you for ur reply sir

[@samiulalim2063]

Thank you so very much

[@dribfun2501]

I curious the first guess from casio It's random right? if I guess better, it take time to solve less than casio guess ?

[@scottcollins7513]

The better the initial guess you supply to the calculator, the quicker it can typically find the correct answer. But, with simple algebra equations like the one in my example, it is going to quickly find the correct answer regardless of your initial guess. The more complex the equation, the more helpful the initial guess. It helps if you know that you want a postive answer vs a negative answer. Or a very small number (like 0.01) vs a very large number (like 200,000).

[@masterpotato2162]

Thank you so many videos to get to this simple solution

[@scottcollins7513]

Glad it was helpful to you, Master Potato. Yes, having access to the world's knowledge frequently makes it difficult to find what you actually are looking for!

[@fmharits3224]

Thank you so much, this will help me a lot

[@scottcollins7513]

Glad it was helpful. Thanks for leaving a comment, Fadhil.

[@tahasinarahmanrimi3204]

If there are x, y two variables , then what should be done?

[@scottcollins7513]

Can you give me an example of what you mean? It depends if you are talking about something like y=3x-5 or if you have two different equations like 2x+y=7 and 3x-2y=11.

[@barambahadurbhandari6279]

I have problems in the bottom which are not working and bottom or key which are not working are bin hexa octa inte log ...now what to do..

[@scottcollins7513]

Make sure you are in the "Calculate" mode -- go to MENU then select "1".

[@john97ls1]

Can you do it on the CASIO fx-83GTX Classwiz? Thanks

[@scottcollins7513]

Thanks for the suggestion, John. I may do a video on the fx-991CW, but I doubt I am going to get to the fx-83GTX. There are just so many slightly-different models made by Casio for different markets. Plus, I am not doing many new videos these days. Regardless, I do appreciate you leaving a suggestion -- it is helpful!

[@luqkiiim]

say i have a complex equation like (9+x)(81-x^2)=864. How do i solve that, but without using the polynomial function? Since using the polynomial function, i would have to first expand the equation which I'm too lazy to do.

[@scottcollins7513]

We know this is a 3rd degree polynomial which means it will have 3 roots (since you have a 1st deg polynomial times a 2nd deg polynomial). Since the solver is using "guess and check" method, it is going to tend to find a root that is closest to your initial guess. You will have no trouble finding ONE of the three roots. The difficulty is going to be finding the other two. You can play around with the initial x guess and see what happens. With your particular example, which has a root x=-15 and a double root x=3, I cannot get my TI-36X Pro to find the x=3 double root. It will only find the x=-15, unless I happen to put in a guess like x=3.01. Even w/ a starting guess of x=4 causes the calculator to find the x=-15 root. You may have to FOIL, my friend, and use the root finder functionality.

[@odarge]

@scott Collins, my HP 48GX can't find exactly 3 with the Solve, it gives an "Extremum" (which it is also) = 2.99998192115. Guess=2. Prime gives also something like 2.999985. In CAS, solve find it (them!) properly. DM42 ("high precision") find and displays an Extremum "3" but shows many 9 when Show is invoked. Cleaner though. DM15L find 2.99991, starting from 2 as guess (same guess than calculators above). Useless but fun ;-) I think the Solver is far from 3, even with the Prime, strange enough.

[@pathfinder5190]

Why do i need to guess a value for x? And does it matter what value I choose?

[@scottcollins7513]

It depends. If it's a relatively simple equation, then you probably do not need to supply a guess for x -- you can likely just use what is already stored in x and go from there. But, there are situations (e.g. trig equations, logarithms, exponentials) where the calculator is unable to find an answer without an initial guess that at least gets it started in the right ballpark. In the end, as long as the calculator says "L-R = 0" below the answer it gives, you do not need to do anything different -- it found a correct solution.

[@tedyscollege]

Thank you so much!

[@scottcollins7513]

Happy it helped!

[@tunseducation2561]

why you didn't use that minus button there?

[@scottcollins7513]

Negative key is for making coefficients negative. Minus button is for subtraction. There are subtle differences between their behavior, so it is good to do your best to use each one for its intended purpose.

[@junix199]

ty

[@rishavsingh2010]

Please may you do a video using a sharp Dal solver there's nothing on KZbin went through alot of videos an example 5+x/30 -30

[@scottcollins7513]

Is this video helpful? kzbin.info/www/bejne/rKO1npV-hZ6tiKM I am not familiar with what SHARP "Dal solver" is. Is it the same kind used on the calculator shown in the video link I shared?

[@Rasha.Hussein44]

Hi is this calc allowed on the college algebra clep ?

[@scottcollins7513]

No, unfortunately. Here is a link w more info: clep.collegeboard.org/test-day/calculators

[@momochanya]

do i need some special set up for this ? because i tryna solve one equation and the answer came out as x=0 when i type 1 and press equal again the whole page disappear 😭 this happen to my friend’s too

[@scottcollins7513]

What eq are you trying to solve? My best guess is that the calculator is having trouble finding the solution and the screen goes blank while it is trying. How about trying something simple and see if you can get it to work ---- 3*x=18

[@rokopavic644]

@@scottcollins7513 yupp still not working for me...

[@scottcollins7513]

@@rokopavic644 STRANGE. I have no idea why it is not working the same as mine. One thing to check would be to confirm that you are in the normal (not complex) mode --> Press "MENU" button and select option 1.

[@PetarOparusic07]

This was really helpful thank you, but i still have a problem. When solving an equation like x(x-2)(x+1)(x+2)=24 i only get 1 answer when there should be 4. Could you help in any way?

[@scottcollins7513]

Glad it was helpful. Yes, you've hit on the problem w using an iterative solver - it only finds the first answer it stumbles across. You can try starting w a different initial guess -- like start with x=9999 and see what it finds. Then try x=-9999 and see. The only way I know to actually find the three roots w certainty would be to rearrange the equation into ax^3+bx^2+cx+d=0 but that requires a lot of tedious expansion.

[@lxnersnotthere8939]

( 5×2-7=3 ) ( 3×2+9=15 ) mustn't the two side equal the same ?

[@scottcollins7513]

Yes, they must be. However, the right side equation is “-3x+9” (negative 3). If you make the correction, plug in x=2, and you’ll get the same answer.

[@masmf.f4122]

Yooooo big helpppp thanks mannnn

[@mostofabanuchy9196]

I had so much syntax error thank you so much brother

[@scottcollins7513]

Always happy to hear when someone benefited from a video. Thanks for letting me know.

[@tunseducation2561]

will it work for x^2 -2x +4=0 this eqn ??

[@scottcollins7513]

Potentially, but it is like using a wrench to pound in a nail -- it might work, but it is not the tool for the job. When dealing w/ quadratic equations, you would be better served by the poly solver --> kzbin.info/www/bejne/rKK0dmaprpWSfpo

[@rojagantasala2145]

How can i find 2 values in an equation like 5x-9y+3=0 and 3x-10y+9=0...My casio was fx-991EX

[@scottcollins7513]

Hello. Watch this video: kzbin.info/www/bejne/fJOnqqaKdtqGoMU One thing you will need to do is to "move" the constant to the other side of the equal sign. In other words, you first need to reorganize the equations to be: 5x - 9y = -3 and 3x - 10y = -9 . The constant always needs to be isolated.

[@donmarco1]

Grande scott

[@scottcollins7513]

Gracias!

[@benzeltser9851]

YESSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

[@8NOOR_]

What if we put an equation which has 2 answers for X? It only shows one answer.

[@scottcollins7513]

You can use the initial guess for x to increase the likelihood of it finding the other answer. Alternatively, you can use the quadratic solver to find both roots.

[@afiamubashira4474]

Which mode is it?

[@scottcollins7513]

Just the standard mode: Menu, 1

[@saikat3020]

is it possible to solve this type of equation with complex numbers like, (8+j5)-x=(5+j4.48)?

[@scottcollins7513]

I don't have the 991EX in front of me to check, but to the best of my knowledge it is NOT capable of solving an equation involving complex numbers.

[@saikat3020]

@@scottcollins7513 yea, I tried and failed with 991 ex. is there any other way to solve this type of equation with a single variable directly?

[@scottcollins7513]

@@saikat3020 Not that I know of, but I'm guessing that a CAS calculator can solve equations with complex solutions.

[@civil7813]

6.25 ans

[@RandomGuyofc]

Can you tell me why mine says x=4 on every equation that I do?

[@scottcollins7513]

That is the calculator's starting guess (you can change it if you want). You need to hit = key again to get it to actually start solving.

[@RandomGuyofc]

@@scottcollins7513 Yea, thx. I searched it up already, but thanks for the answer. But it feels a little bit stupid that it works like that.

[@blacklemon10]

you can use the minus button as negative it does not make a difference .

[@scottcollins7513]

I think most of the time you get away with it, but it is a bad habit. For example, in normal mode, if you use subtract (minus) key to enter -6, the calculator will assume you want "Ans-6" (the previous result minus 6). If you instead use the (more proper) "(-) negative" key, the calculator will simply assume you want "-6". Also, if you switch to a different brand of calculator, you may find it less-tolerant of using subtract key in place of negative key.

[@blacklemon10]

@@scottcollins7513 Interesting, thank you !

[@eduardoramosclamont683]

Is there any way to get procedures?

[@scottcollins7513]

I'm not sure what you mean, Eduardo. Are you asking if it can handle multi-step macros? Or let you save equations/expressions for future use? In my mind it would not matter b/c as soon as the computer is turned off, it "forgets" everything (other than the values stored in variables) that I'm aware of.

[@scottcollins7513]

Or maybe you are asking if it can show the steps used to find the answer -- NO. To get any "steps" you would need a calculator with CAS.

[@sumeadhms3482]

Problem. Why is my calculator showing solved x value as 5 for whatever equation i put. Does it mean my calculator is a fault piece

[@scottcollins7513]

Go to 1:41 in the video. Notice that after it solves you will have "L-R= 0" as the last line on the display. If you instead are seeing "x=5" in black highlight, then you need to hit = (EQUALS) again (maybe even two times). You'll get the hang of it. I really doubt anything is wrong w/ your calculator -- this solver is not intuitive and confuses a lot of people.

[@sumeadhms3482]

@@scottcollins7513 thanks a lot it worked out

[@sumeadhms3482]

But why does it show 46.6 when u hit enter for the first time in ur video?

[@scottcollins7513]

@@sumeadhms3482 The calculator will display whatever value is stored in x at the time. In other words, I probably ran a previous calculation where the solver found x=46.6. That value stays in memory until it is replaced with a new value (even when the calculator is powered off).

[@scottcollins7513]

@@sumeadhms3482 Happy to hear it worked. Thanks for letting me know.

[@nabeeha6033]

Is this allowed in gcse math exam?

[@scottcollins7513]

This video takes a deep dive -- it is 4 years old, so you may want to double check to make sure nothing has changed: kzbin.info/www/bejne/fJaxZoxvhLSCf7M Based on the video, the 991EX would be allowed on the GCSE.

[@hannelius-ze7dc]

why mine always shows x=0 for every equestion

[@scottcollins7513]

Usually b/c you need to hit the equals key one more time to get it to actually solve the problem.

[@jasonkelly6580]

on my calculator (exact same model as yours in this video), for the same equation, my answer is x=2.6

[@scottcollins7513]

Double check that you are entering it correctly and following the same steps. My best guess is that you are stopping before you get to the screen that gives value for x along with "L-R=0" to let you know it found an "exact" solution.

[@waffleisnice]

​@@scottcollins7513 hi ik I'm be late but i also experiencing the same problem. If i don't guess the value of x i get 2 but if i choose to put 1 to guess before the real answer i end up with 2.6

[@scottcollins7513]

@@waffleisnice No idea how/why you would be getting 2.6. Strange. Sorry I cannot help.

[@semanimations5284]

The answer is 2. 5x - 7 = -3x + 9 5x + 3x = 9 + 7 8x = 16 16/8 = 2 X = 2

[@semanimations5284]

​@@scottcollins7513 Your calculator is wrong The answer should be x = 2. Or maybe rec is showing a previous x answer😂😅.. Very tricky

[@DiraLutfiya]

Why mine said the x always equal to zero?? It didn’t work in my calc and i have the same type as u

[@scottcollins7513]

Try hitting the = key one more time.

[@DiraLutfiya]

@@scottcollins7513 still didnt work :(

[@scottcollins7513]

@@DiraLutfiya You’ll probably need to ask a friend or teacher for help. Without seeing the steps you are doing I do not have a practical way to help. Sorry.

[@eiden6744]

I followed the right procedure but instead of 46.77, it gives me 2. How can i fix that?

[@scottcollins7513]

x=2 is the correct solution. The "46.77" is just the value of x my calculator had stored in memory from a previous calculation.

[@zainanbadnan]

❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤

[@scottcollins7513]

Thanks for the love!

[@alexmisra6690]

I'm literally doing the same exact thing. I'm making a one variable equation, pressing shift, then calc, but it's showing a variable error? Is there a reason for this. Someone please help

[@alexmisra6690]

Ok well turns out it only works for the variable X for god knows why, not the other A, B, C, D, E, F, M, Y variables

[@scottcollins7513]

@@alexmisra6690 Glad you figured it out. On the fx-991EX Classwiz, you can solve for other variables. What model are you using?

[@alexmisra6690]

@@scottcollins7513 The Casio 115ES Plus, it's basically the same layout I believe.

[@scottcollins7513]

@@alexmisra6690 Ok, yes -- very similar, but on that calculator you have to tell it what variable to solve for if you do not use X. Let's say you want to solve 3*A=37; you will have to type in 3*A=37,A (the comma "A" tells the calculator it is solving for A). Seems easier to just use X.

[@alexmisra6690]

@@scottcollins7513 Ah, I see. Thank you.

[@menahany3835]

My calculator can't write (x) in example how to solve this problem? 😢

[@scottcollins7513]

What model of calculator do you have? Does it have the "x" button? One thought is that you have it in imaginary mode or some mode that is dis-allowing you to use the x. I'm not sure.

[@ShadowSlimeDEV]

everytime i do it it just says x gratuit s 0

[@scottcollins7513]

Try hitting the = key a second time. You'll know it worked b/c you will see "L-R = 0" at the bottom line on the display. If you are just seeing the "x=0" in black highlight, you need to hit = key again.

[@FatimaZahra-oj5wr]

I hit it again still it doesn't work for me

[@insyirahaeyo]

why my calculator gives me x=0 ?

[@scottcollins7513]

That’s where you put in your initial guess. Hit equals again.

[@oussamazenati759]

Same problem always x

[@english_with_bee]

It workedd!! Thank you!! ​@@scottcollins7513

[@isha8153]

It gives 0

[@xavierdouglas2601]

This calculator can solve for x and y correct?

[@scottcollins7513]

Not exactly sure what scenario you are picturing, but it will solve an equation with multiple variables like "3y=2x-10". You will have to provide a value for x and then tell the calculator to solve for y and it will. Or you can input the value for y and have it solve for x. If you are asking about something different, let me know and I will try to get you an answer. Take care, Xavier.

[@xavierdouglas2601]

@@scottcollins7513 for example 3(x+1)=5(x-2)+7

[@scottcollins7513]

@@xavierdouglas2601 It will do that with ease. I typed it in exactly as you have shown, gave it a starting guess of x=11 (it is rare that this even matters), and had the answer in less than 1 second I would say.

[@xavierdouglas2601]

@@scottcollins7513 when I type an equation in it says it equals to zero am I doin something wrong?

[@scottcollins7513]

@@xavierdouglas2601 Press the = sign one more time and it will probably do the trick. If not, rewatch what I'm doing and be careful to follow every step. I'm pretty sure you are doing something wrong (unless the solution to your equation is actually x=0).

[@tabshirabegum6612]

X= 02, L-R = 0. Is it okay? ?

[@scottcollins7513]

It is giving you the correct answer (not sure why you have a zero in front of the 2, but it's technically still the correct answer). The L-R=0 is just the calculator telling you that it found an answer where the difference between the Left and Right sides of the equation are equal -- in other words it found an answer.

[@mhama8212]

Why my calculator give me x=2 ?

[@scottcollins7513]

That is the correct answer to the equation. If it is giving this to you at the very beginning of the process (see 1:22 in the video here: kzbin.info/www/bejne/pHmphYGnnNN2edk) then it is simply the last value the calculator had for x (from a previous equation or whatever). Hope this helps.

[@isha8153]

Why mines giving 2 😭

[@scottcollins7513]

The most likely culprit is that you forgot to put a negative sign in front of the 3x on the right hand side of the equation.

[@martinemcgilvray9026]

mine says 0 but there is an M symbol

[@scottcollins7513]

The M symbol just means you have something stored in the memory register and does not impact the solver. I think you just need to hit equal button again to get the solver to give you an answer.

[@oussamazenati759]

My calculator gives me x=0 each time

[@scottcollins7513]

You are not alone. There must be something different about some calculators. My best advice is to have you hit the = key an additional time and see if that works.

[@Aahlaad-Robo_Rio]

pls help i am getting the answer as 0

[@Aahlaad-Robo_Rio]

no need i found out how to do it by looking at how you help other people i am very grateful to you

[@filesgamale7412]

answer is 8, used online calculator, and we have extaclty the same calculator

[@scottcollins7513]

Make sure you are putting a NEGATIVE sign in front of the 3 coefficient on the Right-hand side. I think you are likely using POSITIVE 3 and that is what is causing you to get x=8.

[@proskills991]

I keep getting X=0 Please help

[@scottcollins7513]

When people get x=0 (assuming the answer should be something else), they are failing to hit the = sign a second time to get the calculator to actually find the answer. Try hitting that = sign again. Hope it works for you.

[@proskills991]

@@scottcollins7513 THANK YOU SOO MUCH 🙏🙏🙏🙏

[@scottcollins7513]

@@proskills991 Happy to hear that worked. Thanks for letting me know, Proskills.

[@barbievargas2886]

Why does mine says 0? X=0

[@scottcollins7513]

I'm guessing you need to hit the equals key one more time to get the calculator to solve -- hard to tell since I'm not sure precisely what you are describing. Hope this helps, Barbie.

[@barbievargas2886]

@@scottcollins7513 thank you for the response. It says x=0. It is always x=0. I just did what you did. But the answer of my calculator is 0. I tried the other equation but it says 0 as well. Can u tell me what's the problem?

[@barbievargas2886]

@@scottcollins7513 Thank you so much it worked.

[@scottcollins7513]

@@barbievargas2886 Glad to hear you figured it out! I was pretty sure you just needed to press equals key again -- it is admittedly confusing. It is very hard to help w/out being able to actually see the screen.

[@oranbinyaminovich1202]

Not work its write me x=0 on all

[@scottcollins7513]

You need to hit the = sign ONE more time.

[@user-cv2zf2qs2y]

Can some one help me mine its=0 all😭😭😭😭

[@scottcollins7513]

My guess is that you need to hit the equal key again.

[@davidengel3309]

5x-7=-3x+9, but that gives x=2?? Why does it say 46,776…

[@scottcollins7513]

My best guess is that you need to hit = key a second time. You will know it has found the answer when you see “L-R=“ displayed on the bottom line of the display. If your x=46,776 is highlighted in black, then it has not yet found an answer.

[@davidengel3309]

@@scottcollins7513 i meant in the video it says 46,… but it should say x=2 right

[@scottcollins7513]

@@davidengel3309 I see. The calculator will always display the current value of x stored in the calculator. I evidently had done some other problem where the solution was 46….

[@davidengel3309]

@@scottcollins7513 so it defeats the whole purpose of why people are specifically buying this calculator for it’s ability to solve any equation?

[@scottcollins7513]

@@davidengel3309 At 1:40, it shows the calculator coming up w the expected x=2 solution.