Write the equation in vertex form:

Question

y= -3x^2+12x+15

Answer 1

You want to complete the square .....
y= -3x^2+12x+15
= -3(x^2 - 4x + c - c) + 15
= -3(x^2 - 4x + 4 - 4) + 15
= -3( (x-2)^2 - 4) + 15
= -3(x-2)^2 + 12 + 15
= -3(x-2)^2 + 27

You should always check your answer by expanding
the result.

Answer 2

Y = -3x^2 + 12x + 15.
Vertex form: Y = a(x-h)^2 + k.
a = -3.
h = -B/2A = -12/-6 = 2.
k = -3*2^2 + 12*2 + 15 = 27.