Question

Find the axis of symmetry and the vertex of the graph of f(x) = -5x^2 +20x -9.

Answer 1

Axis of Symmetry:

x=2

Vertex:

(2,11)

Explanation:

Finding the derivative:

f'(x)=-10x+20

Setting the slope equal to zero:

-10x+20=0 x-2=0 x=2

Finding vertex:

f(2)=-5*(2)^2+20*2-9

=-20+40-9=20-9=11

(2,11)