5-2x2=-15

Solution for 5-2x2=-15 equation:

5-2x^2=-15

We move all terms to the left:

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

We add all the numbers together, and all the variables

-2x^2+20=0

a = -2; b = 0; c = +20;
Δ = b2-4ac
Δ = 02-4·(-2)·20
Δ = 160
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{160}=\sqrt{16*10}=\sqrt{16}*\sqrt{10}=4\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{10}}{2*-2}=\frac{0-4\sqrt{10}}{-4}
=-\frac{4\sqrt{10}}{-4}
=-\frac{\sqrt{10}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{10}}{2*-2}=\frac{0+4\sqrt{10}}{-4}
=\frac{4\sqrt{10}}{-4}
=\frac{\sqrt{10}}{-1}
$