Question

Explain, in complete sentences, how you would completely factor 20x2 - 28x - 48.

Answer 1

4 (x+1) (5 x-12)

Answer 2

saifoo.khan, I know how to factor, but I just guess and check, is there some way to do it faster? Or not really?

Answer 3

there's something called the ac factoring method

Answer 4

Epaema, sorry i didnt get wht u said!
sorry!

Answer 5

I'm so confuzzled, haha

Answer 6

Why?

Answer 7

Never mind. Haha! :D

Answer 8

I think I'm supposed to use the grouping method :/

Answer 9

so it's called "the ac factoring method"?

Answer 10

thts also grouping!

Answer 11

thts kindda shortcut.

Answer 12

Ok, so it's called "the ac factoring method"?

Answer 13

Yes.

Answer 14

There are a lot of different methods. For this one I would look at the numbers first. It should be apparent that you can factor out a 4 from the numbers:
\[20x^2-28x-48 \Rightarrow 4(5x^2-7x-12)\]
The grouping comes into play because we notice here that 12 - 5 = 7, so we get:
\[4(5x^2-7x-12) \Rightarrow 4(5x^2+5x-12x-12) \Rightarrow 4(5x(x+1)-12(x+1))\]
\[4(x+1)(5x-12)\]

Answer 15

er, that should be " ...we notice here that 5x - 12x = -7x, so we..."
my bad.

Answer 16

Thank you!

Answer 17

I still don't get the grouping part..........

Answer 18

idk why didnt u.