Question

http://www.sketchtoy.com/38637495 How would I factor this? @jim_thompson5910

Answer 1

find two numbers that

a) multiply to -20

AND

b) add to -1

Answer 2

Are there any numbers which are factors of 20 and differ by 1?

Answer 3

-5 and 4 :P

Answer 4

so it factors to (a-5)(a+4)

Answer 5

another example

x^2 + 12x + 20

find two numbers that multiply to 20 and add to 12: the numbers are 10 and 2

so it factors to (x+10)(x+2)