-a^2-15a=0

Solution for -a^2-15a=0 equation:

-a^2-15a=0

We add all the numbers together, and all the variables

-1a^2-15a=0

a = -1; b = -15; c = 0;
Δ = b2-4ac
Δ = -152-4·(-1)·0
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-15}{2*-1}=\frac{0}{-2}
=0
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+15}{2*-1}=\frac{30}{-2}
=-15
$