-7x=2x^2-15

Solution for -7x=2x^2-15 equation:

-7x=2x^2-15

We move all terms to the left:

-7x-(2x^2-15)=0

We get rid of parentheses

-2x^2-7x+15=0

a = -2; b = -7; c = +15;
Δ = b2-4ac
Δ = -72-4·(-2)·15
Δ = 169
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{169}=13$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-13}{2*-2}=\frac{-6}{-4}
=1+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+13}{2*-2}=\frac{20}{-4}
=-5
$