-3y^2+15=-4y

Solution for -3y^2+15=-4y equation:

-3y^2+15=-4y

We move all terms to the left:

-3y^2+15-(-4y)=0

We get rid of parentheses

-3y^2+4y+15=0

a = -3; b = 4; c = +15;
Δ = b2-4ac
Δ = 42-4·(-3)·15
Δ = 196
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{196}=14$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-14}{2*-3}=\frac{-18}{-6}
=+3
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+14}{2*-3}=\frac{10}{-6}
=-1+2/3
$