a^2+6a=135

Solution for a^2+6a=135 equation:

a^2+6a=135

We move all terms to the left:

a^2+6a-(135)=0

a = 1; b = 6; c = -135;
Δ = b2-4ac
Δ = 62-4·1·(-135)
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-24}{2*1}=\frac{-30}{2}
=-15
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+24}{2*1}=\frac{18}{2}
=9
$