(2y+6)(6y-15)=0

Solution for (2y+6)(6y-15)=0 equation:

(2y+6)(6y-15)=0

We multiply parentheses ..

(+12y^2-30y+36y-90)=0

We get rid of parentheses

12y^2-30y+36y-90=0

We add all the numbers together, and all the variables

12y^2+6y-90=0

a = 12; b = 6; c = -90;
Δ = b2-4ac
Δ = 62-4·12·(-90)
Δ = 4356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4356}=66$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-66}{2*12}=\frac{-72}{24}
=-3
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+66}{2*12}=\frac{60}{24}
=2+1/2
$