15a(a-3)=15

Solution for 15a(a-3)=15 equation:

15a(a-3)=15

We move all terms to the left:

15a(a-3)-(15)=0

We multiply parentheses

15a^2-45a-15=0

a = 15; b = -45; c = -15;
Δ = b2-4ac
Δ = -452-4·15·(-15)
Δ = 2925
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2925}=\sqrt{225*13}=\sqrt{225}*\sqrt{13}=15\sqrt{13}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-45)-15\sqrt{13}}{2*15}=\frac{45-15\sqrt{13}}{30}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-45)+15\sqrt{13}}{2*15}=\frac{45+15\sqrt{13}}{30}
$