The Quadratic Formula (Derivation)

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[@AnimusInvidious]

"Then... let everyone else pay attention." Love it.

[@geekyprogrammer4831]

I have completed my Engineering 2.5 years ago and I was really good at Mathematics......but when I see this guy, my mind always blows and I feel dumb lol These students are very lucky to get such a teacher!

[@svnvoo]

well it's never too late. at least you get to experience his classroom videos! :D

[@andrewm6424]

😂 That is the greatest compliment I’ve ever seen online. I work in Accounting. I’m okay at math, but I have no idea how to do Engineering Math. I totally bombed 💣 Geometry. I can not see number problems artistically (which is required for Geometry).

[@NoTimeForThatNow]

Still shocks me to see the behavior of many of the students, they should realize how lucky they are to have a great teacher.

[@ericsills6484]

Unfortunately this isn't the 1970's. He can't just grab a whip and flog these guys :-(

[@AshtonPyr]

@@ericsills6484????

[@animationspace8550]

They're still kids, this is peak behavior in most good classes. You can tell your class is horrible at teaching if they scream and talk back to you.

[@avi12]

Finally, a teacher who doesn't only care about the "How to solve", but also "How did it come to be like this" and "Why is like this"

[@johnpleckaitis2336]

I’m going to school to be an ME. Math is beautiful and simplistically easy. I wish every student here appreciates how this man breaks it down

[@pedrito77]

I am 43, and love math(s). I had a very good teacher in high school. He was great, but not as great as you, still, we respected him so much. I want to thank you for all these videos that bring all that knowledge back to me. Also, now I know what surd means. We don't use that word here in CA.

[@atmajap6339]

Surd is basically another word for irrational number

[@advaitBA]

​@@atmajap6339Not really, pi is not a surd, but it is an irrational number; surd refers to square root or cube root or any kind of root. It is the opposite of power or index.

[@big_brein]

I am shocked. I tried learning by reading my textbook but I got so confused, then I came here and I don't think it could've been explained any better. Thank you sir.

[@KitBunting]

Merry Christmas Eddie, thanks for all the videos. I'll be posting videos for my students this year, do other teachers at your school post videos? Or do you make the videos for all levels?

[@garydunken7934]

Merry Christmas. Congratulations for the Australian of the Year's NSW Local Hero Award.

[@parthnaik1838]

Merry Christmas Mr.Eddie Woo . Appreciating you for your work . Please continue your KZbin videos ,they are a lot helpful to the students .

[@singamar]

Neither our teacher, nor we the students, made a mountain out of a molehill like he is doing here. I must add that he is an efficient teacher who has done wonderfully well in other videos. Even the backbenchers of our class knew how to identify the coefficients a, b and c in a quadratic equation regardless of the way it was written!

[@practicalsoftwaremarcus]

I really enjoy you videos, and I was wondering if you could make some on more advanced topics, like complex variable, fourier transforms, etc.. Would be awesome!

[@dimitris713]

Here in greece the square root of b^2-4ac we symbolize it with the letter Δ(capital letter of delta)and then we say x=-b+-square root of Δ/2a

[@pedrolib]

Jimmarasgreece yup, we do it in Brazil as well

[@laurensjansen8190]

In Holland we give it the letter D (discriminant).

[@沈博智-x5y]

we can also do it here in australia but only when we want to be super lazy. I can only think of one way of using delta instead of b^2 - 4ac and that is when we're trying to prove the quadratic equation has no real roots (or finding what type of roots does the quadratic have: 2 real roots, 1 double repeated root, 2 complex or purely imaginary roots) then we'll use: Δ > 0 (2 real roots) Δ = 0 (1 repeated root) Δ < 0 (no real roots)

[@carultch]

@@沈博智-x5y Delta represents a term known as the discriminant, for that reason. It is a test to tell you what kind of roots the parabola has.

[@freemodegaming4562]

Διακρεινουσα

[@Tristoo]

if 1 billionth of the teachers were like you we'd have colonized the known universe 20 years ago

[@reubenmanzo2054]

I think it's safe to say 1 billionth of the teachers is like Eddie. And his name, funnily enough, is Eddie. This also requires 1 in 8 people being teachers, which I doubt.

[@karthikrajtm2471]

If teachers like you are presente in every school of India then everyone will start loving maths , I say this because I have one like you. I'm in class 10 from INDIA

[@ChipterLP]

I still remember how some gene scientist, as a part of teaching us about genes and GMOs, tried to find the population with a specific dominant gene using this formula but somehow (keep in mind we were 1st grade at high school when she tried to do this, we didnt even know the quadratic formula exists) she forgot how to use it and took an entire hour to finish it. I learned nothing that seminar. Anyway, I really love this, helping me be ahead of class in math just like at middle school.

[@panospg5093]

Eddie please answer im a second year junior high school student. which of your videos you recommend to me to see. I love maths so I want to learn even more than the basics

[@RoseAngella]

Its a shame Mr Woo had to take time to settle some of his students. If he hadn’t had to do that he would have completed the explanation in its entirety and be able to talk more on the operations.

[@justinseeberg1996]

Superb.

[@atlegangolifant8674]

Salute Man

[@satyamgupta756]

Where did you teach. Give me some hint regarding your school ar!

[@paulgarcia2887]

"Currently Head Teacher Mathematics in a comprehensive public school in Sydney, Australia. "

[@kaijeong1580]

MERRY CHRISMAS MR WOO!! Thank you for all your videos this year, they helped me alot in tests :))

[@michealwares]

2022 Feb 23 watching this ... thank you... quick question...why can't we take the root of b² at the end of the formula and just get b...like√b²=b

[@carultch]

In the special case that the c-term is equal to zero, you can do that. Because (b^2 - 4*a*c) would reduce to b^2, which means that sqrt(b^2-4*a*c) would reduce to sqrt(b^2), and then to b. Or more specifically, it would reduce to absolute value of b. But since we are applying a +/-, we end up using both -b and +b as part of our solution. Any time c=0 in a quadratic equation, then one of the roots will also equal zero. The other root will equal -2*b. However, in the general case, you cannot do that. sqrt(X - Y) is not the same thing as sqrt(X) - sqrt(Y). So you cannot isolate b^2 to be the only thing under the square root sign, in the event that c is not equal to zero. You might think this also happens when a is equal to zero, but in that case, you wouldn't have a quadratic equation in the first place. You'd have a linear equation. You would also end up with a denominator of zero on the whole thing, which would reveal that the quadratic formula is not a valid way to solve linear equations.

[@danielklein6442]

best teacher

[@suryakandikatla]

I think visual square daigram best derivation for the quadratic formula .

[@Nobody-dg3cl]

Sir.. please make video on engineering mathematics

[@RohanGupta_LP]

Merry Christmas sir. 🎅❄

[@khushisingla496]

Thanq sir i was looking for derivation

[@HarshSingh-us9dv]

Merry Christmas sir.

[@bennykovitz7128]

Yeah... I don't get that "last step." You're not supposed to subtract b/2a from both sides, or else it becomes x = -b/2a +/- sqrt(b^2-4ac) / 2a... Where did I go wrong?

[@playgorund299]

Benny Kovitz I don't see anything wrong. You subtract b/2a at both sides. You get x= (-b ± √b^2-4ac)/2a

[@darkendivine9310]

Is this algebra or something else?

[@paulgarcia2887]

intermediate algebra

[@zainabhasanah]

I wish I had this kind of teacher but then wait I don't even go to school

[@sebastiao1271]

video on how to multiply fractions

[@ismireghal68]

Why cant you leave out the +\- before b^2-4ac but before 4a^2 you can? 9:25

[@antoinevoisin8609]

Because the square root of something can has two results a positive and a negative one

[@Ax2u]

This puzzled me as well. Why is the denominator not +/- 2a?

[@antoinevoisin8609]

You don't need to put the +/- sign unless you do the square root of an equation. For example if i have x^2 = 4, I need to do the square root on both sides of the equation so it will be x = +/- sqrt(4) so the result is x = +/- 2. If you think about it both results are correct since 2^2 = 4 and - 2^2 = 4. That's why you need to put the +/- sign when you do the square root of an equation. Ax2u for your question the +/- is in front of the denominator still. You can see him put the square root on the whole equation than resolving it to get a simplified version of the equation.

[@Ax2u]

I think you're misunderstanding what Ismir meant. The question isn't why you need a +/- sign when taking the square root of an equation, but why the +/- sign seems to disappear as he simplifies the denominator from +/- sqrt(4a^2) to 2a.

[@antoinevoisin8609]

Oh ok in that case the sign is still in front of it it's just that he put it on the top of the fraction instead of the left side.

[@isaseon4097]

4:38

[@sanrihoe3098]

2:06

[@chloefong3031]

Why do teachers not teach this

[@carultch]

#1: proofs are usually available in the textbook to read on your own. #2: they simply don't have time during the term, and have other material that the syllabus requires them to teach #3: it's likely beyond the scope of an Algebra 1 class, since it's usually an Algebra 2 topic to investigate why a formula works I don't know about your classes specifically, but they certainly did teach it for my class in Algebra 2. More like, guided our discovery of it, than taught it directly.

[@agentagrapeseedlingj5647]

woah what

[@sanrihoe3098]

7:33