Find the vertex of the graph of the equation y=-2x^2+18x-15.
I inputed your equation on a special online graphing calculator.
Here you are.
Hope this helps.
Vertex of this dome shaped parabola occurs at the x value = - b/2a = -18/(2*-2) = 4.5
the y value will be
-2(4.5^2) + 18 * 4.5 -15 = 25.5