17-2x^2=-21

Solution for 17-2x^2=-21 equation:

17-2x^2=-21

We move all terms to the left:

17-2x^2-(-21)=0

We add all the numbers together, and all the variables

-2x^2+38=0

a = -2; b = 0; c = +38;
Δ = b2-4ac
Δ = 02-4·(-2)·38
Δ = 304
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:

$\sqrt{\Delta}=\sqrt{304}=\sqrt{16*19}=\sqrt{16}*\sqrt{19}=4\sqrt{19}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{19}}{2*-2}=\frac{0-4\sqrt{19}}{-4}
=-\frac{4\sqrt{19}}{-4}
=-\frac{\sqrt{19}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{19}}{2*-2}=\frac{0+4\sqrt{19}}{-4}
=\frac{4\sqrt{19}}{-4}
=\frac{\sqrt{19}}{-1}
$