-31+16x^2-21=0

Solution for -31+16x^2-21=0 equation:

-31+16x^2-21=0

We add all the numbers together, and all the variables

16x^2-52=0

a = 16; b = 0; c = -52;
Δ = b2-4ac
Δ = 02-4·16·(-52)
Δ = 3328
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:

$\sqrt{\Delta}=\sqrt{3328}=\sqrt{256*13}=\sqrt{256}*\sqrt{13}=16\sqrt{13}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-16\sqrt{13}}{2*16}=\frac{0-16\sqrt{13}}{32}
=-\frac{16\sqrt{13}}{32}
=-\frac{\sqrt{13}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+16\sqrt{13}}{2*16}=\frac{0+16\sqrt{13}}{32}
=\frac{16\sqrt{13}}{32}
=\frac{\sqrt{13}}{2}
$