Question

What are the factors of x2 – 4x – 5? Check all that apply.

Answer 1

When you factor (x^2-4x-5), you get (x+1)(x-5).

Answer 2

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

Explanation:

we have

`x^(2) -4x-5`

To find the factors ------> solve the quadratic equation

equate the function to zero

`x^(2) -4x-5=0`

The formula to solve a quadratic equation of the form
`ax^(2) +bx+c=0` is equal to

`x=\frac{-b(+/-)\sqrt{b^(2)-4ac}} {2a}`

in this problem we have

`x^(2) -4x-5=0`

so

`a=1\\b=-4\\c=-5`

substitute

`x=\frac{-(-4)(+/-)\sqrt{-4^(2)-4(1)(-5)}} {2(1)}`

`x=\frac{4(+/-)√(36)} {2}`

`x=\frac{4(+/-)6} {2}`

`x=\frac{4(+)6} {2}=5`

`x=\frac{4(-)6} {2}=-1`

therefore

the factors are

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