-2x^2+8=-15x

Solution for -2x^2+8=-15x equation:

-2x^2+8=-15x

We move all terms to the left:

-2x^2+8-(-15x)=0

We get rid of parentheses

-2x^2+15x+8=0

a = -2; b = 15; c = +8;
Δ = b2-4ac
Δ = 152-4·(-2)·8
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-17}{2*-2}=\frac{-32}{-4}
=+8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+17}{2*-2}=\frac{2}{-4}
=-1/2
$