-66x(x+1)=0

Solution for -66x(x+1)=0 equation:

-66x(x+1)=0

We multiply parentheses

-66x^2-66x=0

a = -66; b = -66; c = 0;
Δ = b2-4ac
Δ = -662-4·(-66)·0
Δ = 4356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4356}=66$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-66)-66}{2*-66}=\frac{0}{-132}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-66)+66}{2*-66}=\frac{132}{-132}
=-1
$