Question

Which point is the vertex of the quadratic function f(x)=x2−6x+8?

Answer 1

(3,-1)
It needs to be written in standard form before you try to solve it.

Answer 2

Another method!

Pvertex→(x,y)→(4,9)

Explanation:

Given: y=x2−8x+7

This is already in the form  y=a(x2+ba)+c as a=1

So we can do this 'trick'

Applying x vertex=(−12)(ba)→(−12)(−8)=+4

To determine yvertex

Substitute for x=(−4) in the original equation giving:

yvertex=(4)2−8(4)+7

y vertex=+16−32+7=−9