Question

Write the equation of the quadratic function with roots -2 and 4 and a vertex at (1, 9).

Answer 1

Welcome to OpenStudy. I know that since those are the roots, the equation is a product of (x+2)(x-4)

Answer 2

Now, if you plug 1 in the equation, then (x+2)(x-4) = -9

Since you want (1,9) and not (1,–9), then the answer to your problem will be:

–(x+2)(x-4)

Answer 3

Use the 'Mathematics' group for such questions:
http://openstudy.com/study#/groups/mathematics
All the best.