X=y^2-8y+16

Solution for X=y^2-8y+16 equation:

X=X^2-8X+16

We move all terms to the left:

X-(X^2-8X+16)=0

We get rid of parentheses

-X^2+X+8X-16=0

We add all the numbers together, and all the variables

-1X^2+9X-16=0

a = -1; b = 9; c = -16;
Δ = b2-4ac
Δ = 92-4·(-1)·(-16)
Δ = 17
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-\sqrt{17}}{2*-1}=\frac{-9-\sqrt{17}}{-2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+\sqrt{17}}{2*-1}=\frac{-9+\sqrt{17}}{-2}
$