Question

What is the vertex for the graph of y = −3x2 + 18x − 13?

Answer 1

1. You can plug it into a graphic calculator.
2. The x coordinate for the vertex of y = ax^2 + bx + c is x = -b / (2a).
If b = 18 and a = -3, x = -18 / (2•-3) = -18 / -6 = 3
then plug in 3 for x to get the vertex's y coordinate.