Question

Factor completely

10x^2+2x-8
A.) 2(5x-1)(x+4)
B.) 2(5x-4)(x+1)
C.) 2(5x+2)(x-2)
D.) 2(5x-2)(x+2)

Answer 1

B.) 2(5x - 4)(x + 1).

Explanation:

10x^2+2x-8

First divide by the common factor 2:

= 2(5x^2 + x - 4)

Now we factor the expression in the parentheses using the 'ac' method.

5 * -4 = -20 so to get the + x in the middle we need 5x - 4x:

= 2 ( 5x^2 + 5x - 4x - 4)

= 2[ 5x(x + 1) - 4(x + 1)]

= 2(5x - 4)(x + 1) (answer).

Answer 2

B.) 2(5x-4)(x+1)

Explanation:

10x^2+2x-8

= 2(5x^2 + x - 4)

= 2(5x^2 + 5x - 4x - 4)

= 2[5x(x + 1) - 4(x + 1)]

= 2(5x-4)(x+1)