-8x(3-8x)=20

Solution for -8x(3-8x)=20 equation:

-8x(3-8x)=20

We move all terms to the left:

-8x(3-8x)-(20)=0

We add all the numbers together, and all the variables

-8x(-8x+3)-20=0

We multiply parentheses

64x^2-24x-20=0

a = 64; b = -24; c = -20;
Δ = b2-4ac
Δ = -242-4·64·(-20)
Δ = 5696
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5696}=\sqrt{64*89}=\sqrt{64}*\sqrt{89}=8\sqrt{89}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-24)-8\sqrt{89}}{2*64}=\frac{24-8\sqrt{89}}{128}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-24)+8\sqrt{89}}{2*64}=\frac{24+8\sqrt{89}}{128}
$