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

Solution for (3-y)(5y+6)=0 equation:

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

We add all the numbers together, and all the variables

(-1y+3)(5y+6)=0

We multiply parentheses ..

(-5y^2-6y+15y+18)=0

We get rid of parentheses

-5y^2-6y+15y+18=0

We add all the numbers together, and all the variables

-5y^2+9y+18=0

a = -5; b = 9; c = +18;
Δ = b2-4ac
Δ = 92-4·(-5)·18
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-21}{2*-5}=\frac{-30}{-10}
=+3
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+21}{2*-5}=\frac{12}{-10}
=-1+1/5
$