-2x(x-10)=6

Solution for -2x(x-10)=6 equation:

-2x(x-10)=6

We move all terms to the left:

-2x(x-10)-(6)=0

We multiply parentheses

-2x^2+20x-6=0

a = -2; b = 20; c = -6;
Δ = b2-4ac
Δ = 202-4·(-2)·(-6)
Δ = 352
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:

$\sqrt{\Delta}=\sqrt{352}=\sqrt{16*22}=\sqrt{16}*\sqrt{22}=4\sqrt{22}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-4\sqrt{22}}{2*-2}=\frac{-20-4\sqrt{22}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+4\sqrt{22}}{2*-2}=\frac{-20+4\sqrt{22}}{-4}
$