Help with precalc quadratic functions?

Question

Answer 1

A quadratic function in vertex form can be represented as

y = a(x-h)² + kvertex is (h,k)

y = a(x-9)² + 3

since y-intercept is -9, it passes through point (0,-9)

This should satisfy the equation

-9 = a(0-9)² + 3

-12 = 81a

a = -12/81

a = -4/27

so the equation becomes

y = (-4/27)(x-9)² + 3