Quadratic inequalities (visual explanation) | Algebra II | Khan Academy

[@LISA.WANG.]

I was literally having a breakdown looking for any sort of explanation and this nailed it, _thank you_

[@eldrediienecio7904]

(I wear my earphones watching your videos) 5:57 you just blew my eardrums..damn!

[@cheeziipuffs]

Eldred II Enecio "excuse me my throat was dry" You know I had to do it to em XD

[@stormyraine2411]

this comment is written in order to show appreciation for the fact that this video still helps students all over the world even in 2021 and after 2021

[@nocturnalvisionmusic]

Still true in 2022 as well. 😇😌

[@IShowBingChilling]

@@nocturnalvisionmusic still true in 2023 :)

[@nocturnalvisionmusic]

@@IShowBingChilling aww yes :)

[@m.ehsaan.]

As a viewer from 2023, I confirm that.

[@nocturnalvisionmusic]

​@@m.ehsaan.:)

[@velozityzero5161]

*cough* sorry my throats really dry I just ate too many almonds 😂

[@ryanroshan250]

What

[@nocturnalvisionmusic]

5:57 I honestly forgot about this 😂

[@271ivana]

and khan academy once again saves my life. thank you

[@P_fromTheValley]

I really enjoy your videos. Maybe remake this one though :D

[@albertvital383]

My misophonia and that chewing noise made me almost immediately slam my head into the keyboard. 🙃

[@OctavioAlvarez]

Well... solving >0 for F(-x) is numerically the same as

[@jennifercorte3799]

You mean -F(x), not F(-x) in your explanation. F(-x) is a reflection of F(x) about the y axis, and doesn't change which direction the parabola opens. Because of that reflection, however, F(-x) will have the opposite roots of F(x). Since -F(x) is a reflection about the x axis, it has the same roots as F(x).

[@1234cm1]

Thanks man, missed this lesson in class from being sick. Saved me on the exam.

[@MrRnK1]

@1080portal because when you factor you set the two equal to 0. like x+3= 0 and x-2 = 0 and then solve. hope i helped

[@javn4664]

thank you a lot. I watch a bunch of videos but after yours all my confusions become clear

[@aaron5131]

Javokhir Nizomqoriev your life is a confusion.

[@Ian-th3np]

thanks for this stuff, im taking my algebra EOC tomorrow and I think these videos just saved my life.

[@sonicagm]

why would jade have a problem with math?

[@aaron5131]

What life?

[@agusttea8615]

You are a life saver, bless you Mr. Khan!

[@missmusic881]

thank you!!!!! U saved my life. Keep up the good work!!!!!!

[@MoRizz05]

14 years ago!? I just can't believe, I was like 2 years old at that time, how time flies, 2021 anyone?

[@nocturnalvisionmusic]

2022 :)

[@taoistmath]

@digforbear The min point is necessary for this, but not by finding the derivative. the point is to know that the x-coordinate of the vertex is -b/2a, hence vertex is (-.5,-6.25) and not (0,-6) as stated in the video. The comment 'the vertex is the y-intercept' is incorrect and rarely the case. These videos are great to see but please be aware minor errors may exist.

[@antony172]

absolutely agree with you

[@nelsonnie2590]

Thank you Khan Academy 🙏

[@alexk8676]

8:40 that graph makes me sick

[@brandongriggs6934]

Wait but if the coefficient on x is negative then shouldn't it be an inverse parabola?

[@theunknownexplorer1944]

Who is here in 2018? His voice is very young compared to now. :)

[@backupkidus]

Hey man here 2023 u alive 🙁

[@nocturnalvisionmusic]

​@@backupkidusI hope so :( :)

[@maria1239876]

@Ileong862 a little bit yes. it just depends a lot on the high school your going to. people go at their own pace i know juniors and even seniors that are barely learning this stuff.

[@mikkelgreene9065]

Great video!!!

[@pleasedontlookatme78789]

honestly your vids help me so much i love how you cut the crap and teach it as it is like ur the best

[@Megatr0n12]

thanks a lot, i thought i was missing something when the text book started blabbering but you pretty much cleared up my confusion

[@gbberylium]

Thanks...just explained it much better than my teacher...

[@vonFroggula]

This has been the best explanation and I finally understand how to do this! THANK YOU!!!

[@watchutalkingboutwillis3722]

better than yr 10 maths teacher

[@becalmandquiet881]

Great video

[@KristyC]

This actually heled me

[@danjandris]

This is helpful. Thanks.

[@vastthepenguin]

What are you up to after 15 years

[@nitamac1312]

8:32 lines have feelings too!

[@nocturnalvisionmusic]

That was awesome 😆😁

[@natl3118]

You have improved your writing sooo much omg hahah

[@Raiyun166]

thanks. You pretty much own at teaching.

[@SamRobertduty]

Excellent 5/5. Very kind of you to make these videos.

[@vastthepenguin]

What are you up to after 15 years

[@r.vaishnavi7878]

​@@vastthepenguin Exactly.. I wonder what he's doing after 15 years... Successful taking quadratic equations?

[@vastthepenguin]

@@r.vaishnavi7878 exactly right what could he possibly be doing after 15 years dose he have a wife, kids is his family happy how is his life all important questions

[@r.vaishnavi7878]

@@vastthepenguin yeah right 😅

[@vastthepenguin]

@@r.vaishnavi7878 how did you do on your test do you think

[@fahmidameow8529]

i see most of the people making negative comments. y'all so salty. This video just saved my couple of marks!

[@farhadhussain9637]

Nice work

[@CcanCcaglar]

@PLdrummer no a was -1 he multiplied the whole thing by -1 to get 1, that means ur changing the initial graph....

[@spiritblood1100]

i finally understand this, thank you so much

[@2002cc]

samee, IT TOOK ME A FEW HOURS ON REPEAT PLUS PRACTICE TO FINALLY UNDERSTAND THIS OMG

[@annahills342]

So the curve would be determined by the sign in front of C?

[@meanqueen0024]

well here's an idea. you get two roots. put the smaller root on the left then the original inequality sign. then x then the sign again and then bigger number. works everytime. for example. for x2+3x-28

[@idster7]

thank you, sir.

[@spikedog123]

thanks.

[@elementoxygen]

I love watching your math videos 8) ! They're always great

[@bananaking1111]

elementoxygen it’s been 10 years man. How ru

[@xpurefantasy]

Hey man, how has life changed

[@lifesucketh4923]

You alive?

[@vastthepenguin]

How you doing after 14 years

[@AstnPw3rs]

considering the second example say you didn't know how to do it visually. don't you have to test all in intervals? here you only tested values x>4 while i'm at it, can you work a non-factorable quadratic inequality using a non-graphical method?

[@iAmTheSquidThing]

Weird, I was also eating almonds whilst watching this video. Coincidence? Almost certainly.

[@lifetimephysics8308]

U still alive

[@Kayla-jv9xx]

I know I'm 10 years late but ew

[@d00dlefreak]

thank you

[@beingontopper]

congrats ur the first ever commenter🎉

[@mikaelakozechik7345]

"See you in the next presentation" *drops mic*

[@NaimishBaranwal]

please upload modulus quadratic questions

[@thefreakinacage]

thank you so much! -.-

[@user-cx4us5ge4h]

2020 here :)

[@leonjakupi4728]

almost 2021, 0r is it?

[@nocturnalvisionmusic]

@@leonjakupi4728 now 2022 :D Was rewatching a lot of these in 2020 though :3

[@lineekelashangano6322]

Good. But I don't know why the eating is so annoying me😢

[@Pe1Rn]

My problem here is you started with a different concavity, and flipped the greater than to lesser than so you ended up answering the reverse question for the reverse curve??

[@zahrashehryar4637]

This should be solved without changing the inequality sign for the correct set of values, right?

[@SgtPeppersLonelyHeartsClubBand]

sal khan I love you

[@nopekitty]

the goat

[@williamgaw2798]

Is this method (using a graph) the same as using the sign charts method? But like just different styles? Will i get the same outcome or results if i use the sign charts instead?

[@Aryastis]

for (2m-1)x^2-14x+1>0, why is it that b^2-4ac

[@skaplan2]

Isnt the parabola upside down at the end because its a negative in front of x squared?

[@isnansunuyuntaro2974]

Why if you multiplied the whole expression,the inequalities notation changes?

[@KenKoh9801]

@waaathaaa The 3 and -2 are the only factors of -6 that add up to -1.

[@Aryastis]

@theillusion100 thank you for explaining that! (:

[@vipb2utyshawol99]

does the line have to be dotted for the less than or greater than graphs

[@sibusisozuma1944]

How do get a solution for an inequality without roots

[@steve_2157]

wher do u get the s and-2???

[@paulceltics]

@skychy wowowwowowow

[@feero9680]

Finally, now i can rest in peace.

[@adrived]

This video was uploaded before I was even born,

[@nitamac1312]

DARRRRRN YOOOOOOOU ALMONDS!

[@danielmirande377]

pog!

[@CcanCcaglar]

shouldnt the graph be the other way rounnd? because a

[@brii357]

CcanCcaglar ...idk if u still care abt this but he flipped it around by multiplying both sides by -1 which makes a>0 since it is now positive

[@skychy]

8:31 Thats what she said...

[@brownboy6343]

Wait so im confused howw is -28 between -7 and 4?

[@mirzairtiza3620]

-28 is greater than -7 and lesser than -4

[@studyhard7722]

@@mirzairtiza3620 wrong -28 is smaller than -7 and -4

[@ZeetotheAHHH]

Imong mama

[@puja877]

are you the guy that created maths??

[@SgtPeppersLonelyHeartsClubBand]

How do you calculate what the roots are? (x+7)(x-4) Roots: -7, +4. How exactly do these roots work? I have little understanding of them.

[@SeokjinKim]

thx but u can stop to dirnk water if u really need

[@sanju0202able]

shittt..... u coaughed rit to ma ears........... i ws with the headset...... :P bt dt kept us live throught the vedieo... :)

[@FlyWithCheese]

Use the quadratic formula.

[@GndmMkv]

negative six u mean

[@Ileong862]

are you ahead if your learning this in 8th grade?

[@uzma11]

LOOOOOOOOOOOOOOOOOOOOOOOOOOL, ''mty throat is dry, i was eating too many almondss'' :L:L ahahaha ! aahhhh; Mr.Khannnnn u are wiked :)

[@axelcracauer5829]

Sal Khan when he eats too many almonds:

[@fabricioa9782]

I can hear your saliva when you talk.

[@beingontopper]

anyone from 2024??

[@VisualsbyYouri]

@skychy lmao right

[@zeetee6]

whut? whut happened??????

[@dragonbro5532]

I'm sorry, but you don't really explain why you do each step, you just tell us to do certain things, and if you don't really have a good understanding of the subject, you finish the video more confused than you started.

[@Yev371]

at 9:51 I shit my pants!

[@vastthepenguin]

How are you 12 years later

[@xUBERJEWx]

@razmadaz123 rahul, go eat curry :D

[@happyicecream2958]

I’m here from year of pandemic 😷🦠

[@leonjakupi4728]

same

[@jimmyjones2836]

Please for the love of god. pause the video. clear your throat. the last half of this was TERRIBLE to listen to your mouth/throat noises.

[@marin9207]

You didn't even explain the correct way are you serious!

[@jknvorneb]

can you say where's he wrong?

[@grettamunchnick]

There is more than one way to approach several points of math.

[@RuggedCoyote69]

Thank you