The zeros on a parabola are -2 and 4, and the optimal value is 18, what is the equation in factored form?

Question

Help find the equation 

Answer 1

y = a(x-4)(x+2).  The optimal value (maximum) occurs at the vertex, which will have x coordinate 1 because it's midway between the two stated zeros of the function.

 

substitute (1,18) to determine value of a.