What is the vertex form of y=x^2+6x-12?

Set to 0.

X² + 6X - 12 = 0

X² + 6X = 12

Now halve the coefficient of the linear term (6), square it and add it to both sides

X² + 6X + 9 = 12 + 9

factor the left side and gather terms on the right

(X + 3)² = 21

(X + 3)² - 21 = 0 ======Vertex form

(- 3, - 21) ------Vertex of the function