-5y(y-6)=-15

Solution for -5y(y-6)=-15 equation:

-5y(y-6)=-15

We move all terms to the left:

-5y(y-6)-(-15)=0

We add all the numbers together, and all the variables

-5y(y-6)+15=0

We multiply parentheses

-5y^2+30y+15=0

a = -5; b = 30; c = +15;
Δ = b2-4ac
Δ = 302-4·(-5)·15
Δ = 1200
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1200}=\sqrt{400*3}=\sqrt{400}*\sqrt{3}=20\sqrt{3}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-20\sqrt{3}}{2*-5}=\frac{-30-20\sqrt{3}}{-10}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+20\sqrt{3}}{2*-5}=\frac{-30+20\sqrt{3}}{-10}
$