64=8x+2x^2

Solution for 64=8x+2x^2 equation:

64=8x+2x^2

We move all terms to the left:

64-(8x+2x^2)=0

We get rid of parentheses

-2x^2-8x+64=0

a = -2; b = -8; c = +64;
Δ = b2-4ac
Δ = -82-4·(-2)·64
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-24}{2*-2}=\frac{-16}{-4}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+24}{2*-2}=\frac{32}{-4}
=-8
$