Y=x^2-16x=128

Solution for Y=x^2-16x=128 equation:

=Y^2-16Y=128

We move all terms to the left:

-(Y^2-16Y)=0

We get rid of parentheses

-Y^2+16Y=0

We add all the numbers together, and all the variables

-1Y^2+16Y=0

a = -1; b = 16; c = 0;
Δ = b2-4ac
Δ = 162-4·(-1)·0
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-16}{2*-1}=\frac{-32}{-2}
=+16
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+16}{2*-1}=\frac{0}{-2}
=0
$