If x = negative 1 then - x squared - x =? MANY will get this BASIC Algebra Problem WRONG!

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[@bigdog3628]

super simple factor out -1 : y = -1 (x² + x) Next we plug in -1 for each x variable: y = -1 [ ( -1² ) + ( - 1) y = -1 [ 1 - 1] which gives us 0

[@johnmarchington3146]

John, I've been meaning to mention this before. I live in New Zealand and when I went to school many, many decades ago (I'm 86 now) I used to use what I remember as BOMDAS, which stands for Brackets, Of, Multiplication, Division, Addition and Substraction and I don't recall ever learning that the order of Multiplication and Division, for example, should be carried out from left to right if they both exist in an expression. In other words, I remember assuming that if there are both signs in the expression the multiplication would always be done first, regardless. I now realise that this is wrong, but I remain intrigued about what I remember learning..

[@bigdog3628]

it is a huge debate and why I wouldn't be the tiniest bit surprised if people stop teaching pemdas or whatever your nation calls it. (go ahead google pemdas debate or pemdas is wrong)

[@samswift4921]

I never learned PEMDAS or any equivalent system for order of operations. Parentheses were always put in problems.

[@samswift4921]

25

[@johnmarchington3146]

@@samswift4921 If parentheses were present in an expression, I guess almost everyone would instinctively carry out the calculation(s) within them first.

[@johnmarchington3146]

@@bigdog3628 I might be completely wrong in what I'm about to say as I'm not an Excel user, but I wonder if some of those people who are might incorporate algebraic equations that are PEMDAS-based to work through financial statements and if they didn't follow those rules there could be dire consequences!

[@laurendoe168]

First square x. We're doing a replacement for "x" and parentheses are implied: (-1)^2. This equals 1. This is then negated because it was -x^2, which leaves us with -1. We now subtract a -1 from -1 which leaves us with zero.

[@HarryBell-zp8wz]

-2

[@dough9512]

You got the right answer, but your math is wrong! -1-(-1)=-1+1=0. (-1-1=-2)

[@laurendoe168]

@@dough9512 I assure you, my math is correct. Read it carefully. -x^2 = -(-1)^2 = -1 -1 minus -1 = 0

[@laurendoe168]

@@HarryBell-zp8wz No, zero

[@KarlSnyder-jh9ic]

I learned this lesson from one of Tutor John's earlier videos. Good to see I got it. Strange this wasn't stuffed in my head decades ago.

[@donnalannan2978]

I graduated from high school in 1968, i enjoy your videos as i can reflect on lessons learned and relearn things i forgot or never was exposed to. It is fun to try to do the math mentally. Thanks for your videos. I wish they had been available when i was in school!

[@justanotherguy469]

Mr. Math Teacher, is PEMDAS arbitrarily chosen or is there a fundamental approach to its derivation?

[@richardhole8429]

Compared to my age, PEMDAS is fairly recent, however, the order of operations is the same I was taught in the 60s without the mnemonic aid. It may have been arbitrary (it wasn't) but it was necessary to make the definition.

[@garyhempel6316]

the answer in the USA is zero, in Canada it is Zed.

[@stevenjohnson1143]

Plugging in -1 into the equation -1-(-1) since the second negative is cancelled by the subtraction you get -1+1=0

[@awcampbell2002]

I'm afraid that I have had to work equations for too long with various scientific calculators & without parenthesis to disambiguate the -x^2 I could evaluate this in multiple ways to multiple solutions. Negative - negative 1^2 could either be evaluated to positive 1^2 or negative 1^2 negated. If I had been a student in your classroom I would have known which way you expect it to be evaluated, having watched some of your videos I also can guess which way you want this evaluated, but I would prefer that the equation be unambiguous from the start.

[@MargaretCutt-um8iq]

the point was for us to disambiguate the problem. i think it might be important for people who use calculators all the time to brush up on their math skills not using a calculator...... keeps us honest.

[@gavindeane3670]

The equation is completely unambiguous. Any secondary school student who is half way competent at mathematics will be able to draw you the graph of y = -x² and show you that when x = -1 then y = -1. It's just an upside down version of y = x². -x² means "square the value of x then take the negative of the result". Negation is a lower precedence operation than exponentiation. If that were ever to change then the entire way we write polynomials in mathematics would be turned on its head.

[@awcampbell2002]

@@gavindeane3670 Thanks for this comment, unfortunately I had differing interpretations of negating things with multiple instructors as I grew up. You just had to learn the way they meant you to interpret the sign (one said if the dash is above {think superscript} it meant negative numbers, if it was on the same line as the numbers it meant minus). I haven't seen that interpretation after that instructor, but always kept it in mind in case it was the proper method. Reverse Polish notation (HP calculators early on at least) had its own challenges. Casio interpreted one way, TI another, so I was unable to figure out what was the correct way based on observation. I may have inadvertently taught this the wrong way while I'm the army teaching basic electronics (ohms law, phase angles etc for DC or for AC circuits) because the post exchange sold 1 brand of calculator & so I would show the steps needed to get the correct answer for the problems given. Since the students had the same calculators they got the same results which made me think I had finally gotten this down to a science. The way this problem was written is not the way I would have written it. I would have put parentheses around the x^2 excluding the negative sign to ensure the students knew which operation to do first (this was how it would have to be entered in the calculator too). This gave the students the best chance to learn the underlying concepts for the circuits without tripping up on the math. Most of our lesson plans reflected the same thing, we didn't want to fail someone because of math when they might be an excellent repairer after getting past theory & into the practical work.

[@awcampbell2002]

@@MargaretCutt-um8iq Having taught basic electronics in the army any test questions we wrote would not have been allowed with the multiple possible interpretations this problem could evoke. While growing up my math instructors would say one way one year, the next instructor would say the opposite the next. You learned to interpret based on who was teaching each class in which way they expected you to respond. While teaching in the army the exchange has only 1 kind of scientific calculator, I taught based on how the calculator was programmed to respond. This allowed the students to learn the concepts of electronics (very basic ohms law, phase angles stuff) without trying to figure out the math. The occasional student who bought a calculator on the economy (outside the exchange system) would present a challenge trying to figure out how their calculator took in/processed & gave out the answers. HP with its reverse Polish logic for example but Casio did it differently than TI too. The only way to disambiguate was to be very specific in how you presented the math, use of the parentheses was not assumed but given to the students on their tests. This gave the students the best chance to show their mastery of the concepts rather than bog down the critique time with explanations of why a particular student missed a particular question where the data entry was the same, but the results were not. I was the instructor that never had pre-existing questions written into notes on my lesson plan, this precluded the students sneaking up to my lectern during breaks to get the answers, I created the problems on the board each time without a calculator but ensuring the question would come out fairly even in the end. (Memorized many fractions decimal equivalents to make it happen for parallel and series parallel circuits for example). If the student failed out they had a real (non-zero) chance of being changed to 11B (infantry) and although Vietnam was over there was no guarantee there would not be another conflict pop up. I gave my best to keep people in class & on track to become electronic repairers. This included disambiguation of questions of numbers.

[@MrSummitville]

​@@awcampbell2002 And now, you finally learned the correct way!

[@Geoff_G]

-x²-x= Given x=-1 Substitute in --1²--1=

[@raya.pawley3563]

Ouch! Thank you I read that as -(-1^2) - 1; doing the exponent first. Then the multiplication of -1 times the square of -1; or -1*1. Finally, the add/subtract, -1 -1 = -2 -(-1*-1)-1 = -(1)-1 = -2

[@user-gj3ty6xe6h]

You probably only did it that way because that is the way he has told us all to do it multiple times in the past! It was incredibly naive of you to assume that he would expect you to calculate it similarly this time. You should have known better. The actual correct way to do it is exactly the way you did it, but I have learned from many examples in the past on this channel (when presented with squares of number that have a "-" in front of it) that the best way to arrive at the same answer he comes up with is to skip ahead in the video to see what he wants us to do in THIS particular instance.

[@joepkortekaas8813]

Alas.you're wrong -it's zero!

[@dough9512]

Your final equation is improperly stated. It should be -1-(-1)=0.

[@raya.pawley3563]

@@dough9512 you're correct. Dropping a sign is my most frequent error. Took me a few extra minutes to find it. It is easier to keep the signs in order on paper, rather than in my head. Thanks!

[@gopherspace8571]

Thanks Mr J I can't believe it but I got this right 👍 Because of your lessons. I can never thank you enough. I'm gonna give you onna these ❤ and onna these 😎👋💪🙏🌎 I needed math so bad today 😂 I have a serious math problem I'm addicted to math so bad 🤣 and your my guy Mr J. You gave me math on a Sunday night ❤ And I was desperate . Good stuff really good stuff 👍

[@alexandrabloch1687]

Good morning shalom everyone

[@chrisdissanayake6979]

Please be patient and let Mr John teach. Let’s remember that this is Mr John’s class, not yours or mine.

[@redblack8414]

@chrisdissanayake6979 I totally agree with you.

[@chrisdissanayake6979]

Thank You 🙏🏽

[@franklinbrown5625]

-1(-1)^2-(-1)=-1(1)+1=-1+1=0

[@raya.pawley3563]

Thank you! I see my error now. I dropped the sign on the right hand variable

[@maxinemcafee4893]

a) 0

[@russelllomando8460]

Got it 0 fun with the negative signs. thanks for the fun.

[@samswift4921]

Correct. That is what our math teachers wanted us to do.

[@niranjanchakraborty1139]

Ans=-0. --(--1)^2--(--1)=--1+1=0

[@bigdog3628]

did you honestly say negative zero? No such thing as negative zero

[@mossesmadjemite2289]

C) -1

[@dough9512]

The answer to the equation is 0. The answer to the problem is a).

[@katharinetheresa4842]

I came up with 0

[@alessioandreoli2145]

A

[@samswift4921]

A This was difficult to figure.

[@sekharb6651]

-2

[@anastasiospapandreou147]

0

[@Ca_milo_G]

2

[@erniemorris9991]

0 factor out the negative

[@benquinneyiii7941]

A double negative

[@dough9512]

But, a double negative is NOT proper English!!

[@mariao.patino7259]

- (-1)2😮

[@mahamunibalakrishnan8263]

C.-1

[@mahamunibalakrishnan8263]

A) 0

[@jamesmoyles8494]

d

[@georgitetuc]

My god , is it for the nursery school ?

[@debbieholoquist2059]

Yes, it's a very basic problem. But look how many here got it wrong.

[@georgitetuc]

@@debbieholoquist2059 yes , it’s unbelievable :)

[@davidtuer5825]

23 minutes to explain the obvious. He managed to spread confusion, It seems that "correct" maths is decided arbitrarily by some committee or other.

[@rajalakshmik6148]

0 is correct

[@lynneareckson2166]

try, try again.........

[@rgrinnell]

D

[@erembald2927]

I get 2

[@JosieGodfrey-ph8sg]

A) 0

[@fubaralakbar6800]

PEMDAS=Please excuse my dumbass student

[@debbieholoquist2059]

🙃

[@subhashchatterjee7627]

Answer is a i e 0

[@jerryanstey7058]

Most people bragging here probably never got this ! 🤓

[@gregwessels7205]

"Stumbling and bumbling over my words" - and that's why you teach Math.😂

[@CHONGKEEHo]

⁰

[@cyn4rest]

Zero

[@paulelliott5244]

man do you say a lot of words to get a point across. 20 mins of repetition and 3 min of useful info

[@chrisdissanayake6979]

Could you please understand that there are other students who are slow in learning, unlike you. We really benefit from Mr John’s long explanation. So, please have some compassion about us and learn to tolerate. In life, everything does not happen to please everyone at the same time. This life is very short. Maintaining harmony with others is a praiseworthy quality!

[@carlsendecuba8268]

Stop talking soo much and get to the point. You are wasting our time.

[@redblack8414]

@carlsendecuba8268 Solving a problem and teaching how to solve it are two different things. It takes time to teach how to correctly do something.

[@chrisdissanayake6979]

Please be appreciative and kindly stop your RUDE behavior.

[@garystrittmater8258]

The answer is 0, get to the point!

[@shanoxyshanoxy1230]

Rude

[@tallysom713]

He has to explain

[@mylittlepitbull3143]

You are pretty rude.

[@richardhole8429]

If your point is that you didn't need to attend the class, then you are most welcome to skip it. Fast forward to the end to check your answer. If you can teach better, perhaps you could start your own channel.

[@redblack8414]

@@richardhole8429 Well said. I couldn't have said it better. 👍 Also, one is always free to go elsewhere when not happy.

[@josephlaura7387]

a) 0

[@Krishna-rq6ul]

-2

[@bobbresnahan8397]

d

[@chrisdissanayake6979]

0

[@lynneareckson2166]

-2

[@nancyfloyd7052]

-2

[@pjfreeman4789]

0

[@kennethhubbard2027]

-2

[@kennethhubbard2027]

25

[@kennethhubbard2027]

-(-1)square -(-1)=0

[@hendrikvan3411]

0

[@shariqanasreen4242]

0

[@ravinderjohal1088]

0

[@ThomasGallacher-uj7vs]

0

[@cnfigueira]

0

[@alexandrabloch1687]

0

[@farjanajahan3222]

0

[@user-jj3hi3gh4u]

0

[@rajeshvyas934]

0

[@alexandrabloch1687]

0

[@user-vp5ux5dh9x]

0

[@Sunspot1225.]

0

[@subasu478]

0

[@luillierstephane1463]

0