Another method!
Pvertex→(x,y)→(4,9)
Step-by-step 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