Question

Factor x^2 + x - 20.

Answer 1

When factoring polynomials like this, you want to find factors of the c-value (in this case, -20), that also add up to the b-value (in this case, 1).
What are the factors of -20?

Answer 2

-1 -2 -4 -5 -10 - 20

Answer 3

True, but also the positive values of those numbers. So the factors would be:
\[\pm1,\pm2,\pm4,\pm5,\pm10, \pm20\]

Answer 4

Okay, so what two factors that equal -20 also add up to 1?
For example, \(-1\times20=-20\), but \(-1+20\neq1\)

Answer 5

I honestly have no idea lol.

Answer 6

Well, you automatically can eliminate factors +-2 and +-10 because there is no way those numbers, which are so far apart, could ever add up to 1. So, what factors are you left with?

Answer 7

5 and 4

Answer 8

Correct. Since -20 is negative, you have these two pairs that equal -20 when multiplied:
\(-4\times5\) and \(4\times-5\)
Which pair adds up to 1?

Answer 9

the first one?

Answer 10

good job

Answer 11

so it'd be (x-4)(x+5)?

Answer 12

i belive it is

Answer 13

but i am not 100% sure

Answer 14

thank youuu

Answer 15

Yep, perfect

Answer 16

You're welcome. :)

Answer 17

then great job

Answer 18

you two