-5x(x+6)-10=10

Solution for -5x(x+6)-10=10 equation:

-5x(x+6)-10=10

We move all terms to the left:

-5x(x+6)-10-(10)=0

We add all the numbers together, and all the variables

-5x(x+6)-20=0

We multiply parentheses

-5x^2-30x-20=0

a = -5; b = -30; c = -20;
Δ = b2-4ac
Δ = -302-4·(-5)·(-20)
Δ = 500
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:

$\sqrt{\Delta}=\sqrt{500}=\sqrt{100*5}=\sqrt{100}*\sqrt{5}=10\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-10\sqrt{5}}{2*-5}=\frac{30-10\sqrt{5}}{-10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+10\sqrt{5}}{2*-5}=\frac{30+10\sqrt{5}}{-10}
$