(-6a-5)(a+5)=0

Solution for (-6a-5)(a+5)=0 equation:

(-6a-5)(a+5)=0

We multiply parentheses ..

(-6a^2-30a-5a-25)=0

We get rid of parentheses

-6a^2-30a-5a-25=0

We add all the numbers together, and all the variables

-6a^2-35a-25=0

a = -6; b = -35; c = -25;
Δ = b2-4ac
Δ = -352-4·(-6)·(-25)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-35)-25}{2*-6}=\frac{10}{-12}
=-5/6
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-35)+25}{2*-6}=\frac{60}{-12}
=-5
$