Factoring quadratics as (x+a)(x+b) (example 2) | Mathematics II | High School Math | Khan Academy

Sal factors x²-3x-10 as (x+2)(x-5) using the sum-product form: (x+a)(x+b)=x²+(a+b)x+a*b.

High School Math on Khan Academy: Did you realize that the word "algebra" comes from Arabic (just like "algorithm" and "al jazeera" and "Aladdin")? And what is so great about algebra anyway? This tutorial doesn't explore algebra so much as it introduces the history and ideas that underpin it.

For free. For everyone. Forever. #YouCanLearnAnything

[marksteelman]

I teach that unless you can see the numbers you need right away, prime factorization of the last number is useful in discovering the needed numbers.

[EndureTemptation]

Where did he get 4 and 10 out of @ 1:27? I understand that in this example that may seem quite obvious, but what about when we're confronted with large and unfamiliar numbers?

Answer @ 3:34 "You just have to try these numbers out" doesn't quite satisfy me. The method of "You just have to try these numbers out" isn't applicable.

[mxpvill]

thank you so much khan academy, i love your content you really inspire me to learn more on math

[AmericanCube]

I'm only 6 grade and I have a worksheet about factoring things(my math teacher gave me)
And this really helps a lot! Thanks!

[XtremeGamerPro]

Gosh, 0 likes, dislikes and comments???
I thought more people watched Sal.

[charrrrman]

How has no one called out the error in this mans factoring???? it should be (x+10)(x+4) were (x+10)=0 and (x+4)=0, x=-10 and x=-4. The same for the second one.