15x-15=-4x^2

Solution for 15x-15=-4x^2 equation:

15x-15=-4x^2

We move all terms to the left:

15x-15-(-4x^2)=0

We get rid of parentheses

4x^2+15x-15=0

a = 4; b = 15; c = -15;
Δ = b2-4ac
Δ = 152-4·4·(-15)
Δ = 465
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-\sqrt{465}}{2*4}=\frac{-15-\sqrt{465}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+\sqrt{465}}{2*4}=\frac{-15+\sqrt{465}}{8}
$