Question

Which statement about y = x2 + 3x - 18 is true?

O A. The zeros are -3 and 6, because y = (x - 3)(x + 6).
O B. The zeros are -3 and 6, because y = (x+3)(x-6).
O C. The zeros are 3 and -6, because y = (x - 3)(x + 6).
O D. The zeros are 3 and -6, because y = (x+3)(x - 6).

Answer 1

C

Explanation:

first of all, the correct factorization is

y = (x - 3)(x + 6)

because when we do the multiplication

y = x² + 6x - 3x - 18 = x² + 3x - 18

and then, the factorization tends us also directly the zero points, because y is only 0, when one of the factors is 0.

so, either x-3 or x+6 has to be 0 to make the whole expression 0.

and that is only for x=3 or x=-6