Question

y = x2 − 4x
What is the vertex?

y = −2x2 + 8x − 12
What is the vertex?

Answer 1

Find the x coordinate of the vertex using x =-b/2a
Plug that in for x to find the y coordinate of the vertex.

Answer 2

Or you could complete the square and put the equation into the form:
\[y=(x-h)^2+k\]