Question

Four is a zero of the equation x^3+3x^2-18x-40=0.

Which factored form is equivalent to the equation?

I appreciate any help! Thanks :)

Answer 1

If 4 is a root, then a factor must be x - 4.

Only choices A and D have x - 4 as a factor.

Now look at the constant term of each binomial in the factorizations of choices A and D.

A.: -4, 4, 5

Their product is -80.

The constant term of the original polynomial is -40, so this factorization cannot be correct.

D.: -4, 2, 5

Their product is -40.

This is the correct factorization.

Answer: D.