Which are factors of x2 - 4x - 5? Check all that apply.

1.) (x - 5)

2.) (x - 4)

3.) (x - 2)

4.) (x + 1)

5.) (x + 5)

1.) (x-5) and 4.) (x+1). Factoring works as follows: x*x = x^2 and x*1=x and - 5*x=-5x and - 5*1=-5. So you then have, x^2+x + (-5x) + (-5), therefore, you get the original: x^2-4x-5. This is how factoring works. You could not have x-4 or x-3 for various reasons, including the fact that the only factors of 5 are 5 and 1.

We have been given a quadratic formula. we need to find the factors. the factors are multiplied by each other and gives rise to the quadratic formula

x² - 4x - 5

to find the factors we need to multiply x² by - 5 = - 5x²

then the factors of 5x² should add up to - 4x.

possible factors of 5x² are 1x and 5x.

to get a negative product one factor should be positive and other factor should be negative. the sum of the factors is - 4x, then the larger factor should be negative.

From 1x and 5x, larger factor is 5x therefore it should be - 5x.

sum of 1x and - 5x is - 4x.

we write - 4x in the quadratic formula as (1x - 5x)

x² + 1x - 5x - 5

taking the common factors out

x (x + 1) - 5 (x + 1)

(x-5) (x+1)

therefore factors are (x - 5) and (x + 1)

answers are 1) and 4)