64=x^2-12x

Solution for 64=x^2-12x equation:

64=x^2-12x

We move all terms to the left:

64-(x^2-12x)=0

We get rid of parentheses

-x^2+12x+64=0

We add all the numbers together, and all the variables

-1x^2+12x+64=0

a = -1; b = 12; c = +64;
Δ = b2-4ac
Δ = 122-4·(-1)·64
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-20}{2*-1}=\frac{-32}{-2}
=+16
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+20}{2*-1}=\frac{8}{-2}
=-4
$