2x^2-15=-5x

Solution for 2x^2-15=-5x equation:

2x^2-15=-5x

We move all terms to the left:

2x^2-15-(-5x)=0

We get rid of parentheses

2x^2+5x-15=0

a = 2; b = 5; c = -15;
Δ = b2-4ac
Δ = 52-4·2·(-15)
Δ = 145
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{-(5)-\sqrt{145}}{2*2}=\frac{-5-\sqrt{145}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+\sqrt{145}}{2*2}=\frac{-5+\sqrt{145}}{4}
$