Question

Find the vertex of the parabola whose equation is y=-2x2+8x-5

Answer 1

Given equation is $y= 2x^2 + 8x - 5$

To find the x coordinate of vertex we use formula

$x=\frac{-b}{2a}$

From the given equation a= 2, b= 8  and c= -5

Plug in all the values

$x=\frac{-8}{2*2}=-2$

The x coordinate of vertex is x=-2

To find y coordinate of vertex we plug in -2 for x in the given equation

$y= 2x^2 + 8x - 5$

$y= 2(-2)^2 + 8(-2) - 5= 8-16-5=-13$

So vertex is (-2,-13)