-(-x^2-5x)-5(-x^2-5x)=0

Solution for -(-x^2-5x)-5(-x^2-5x)=0 equation:

-(-x^2-5x)-5(-x^2-5x)=0

We multiply parentheses

-(-x^2-5x)+5x^2+25x=0

We get rid of parentheses

x^2+5x^2+5x+25x=0

We add all the numbers together, and all the variables

6x^2+30x=0

a = 6; b = 30; c = 0;
Δ = b2-4ac
Δ = 302-4·6·0
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-30}{2*6}=\frac{-60}{12}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+30}{2*6}=\frac{0}{12}
=0
$