math
posted by Jane .
Marna wants to find the values of x for which the funciton below will have a value of 10. f(x) = x^2 + x  20. Which of the following shows the correct factorization of this funciton for f(x) = 10.
A. (x + 5) (x + 4) = 10
B. (x  5) (x  4) = 10
C. (x + 6) (x  5) = 0
D. (x + 5) (x  6) = 0
Please explain how you reached that answer.

f(x)=10=x^2+x20
x^2+x30=0
(x+6)(x5)=0