-3(5x-10)x=-66

Solution for -3(5x-10)x=-66 equation:

-3(5x-10)x=-66

We move all terms to the left:

-3(5x-10)x-(-66)=0

We add all the numbers together, and all the variables

-3(5x-10)x+66=0

We multiply parentheses

-15x^2+30x+66=0

a = -15; b = 30; c = +66;
Δ = b2-4ac
Δ = 302-4·(-15)·66
Δ = 4860
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:

$\sqrt{\Delta}=\sqrt{4860}=\sqrt{324*15}=\sqrt{324}*\sqrt{15}=18\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-18\sqrt{15}}{2*-15}=\frac{-30-18\sqrt{15}}{-30}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+18\sqrt{15}}{2*-15}=\frac{-30+18\sqrt{15}}{-30}
$