9=x^2-16x+64

Solution for 9=x^2-16x+64 equation:

9=x^2-16x+64

We move all terms to the left:

9-(x^2-16x+64)=0

We get rid of parentheses

-x^2+16x-64+9=0

We add all the numbers together, and all the variables

-1x^2+16x-55=0

a = -1; b = 16; c = -55;
Δ = b2-4ac
Δ = 162-4·(-1)·(-55)
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-6}{2*-1}=\frac{-22}{-2}
=+11
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+6}{2*-1}=\frac{-10}{-2}
=+5
$