Question

What is the vertex of f(x)=-2x^2+20x-7

Answer 1

You can use the formula
x = -b/2a
After finding x, plug it back in to the function to find y.
x = -20/-4 x= 5
y = -2(5)^2+20(5)-7
y = -50+100-7
y = 43
(5,43)

Answer 2

We have to convert this equation (which is called as standard form) into vertex form. We can do that by completing the square.
f(x) is also known as y, so I will make y equal to 0.

$y= -2x^{2} +20x-7$

$7=-2 x^{2} +20$

$107=(x+5) ^{2}$

$0=(x+5)^{2}-107$

And so the vertex would be (-5, -107)