9^2-2=x^2

Solution for 9^2-2=x^2 equation:

9^2-2=x^2

We move all terms to the left:

9^2-2-(x^2)=0

We add all the numbers together, and all the variables

-1x^2+79=0

a = -1; b = 0; c = +79;
Δ = b2-4ac
Δ = 02-4·(-1)·79
Δ = 316
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:

$\sqrt{\Delta}=\sqrt{316}=\sqrt{4*79}=\sqrt{4}*\sqrt{79}=2\sqrt{79}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{79}}{2*-1}=\frac{0-2\sqrt{79}}{-2}
=-\frac{2\sqrt{79}}{-2}
=-\frac{\sqrt{79}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{79}}{2*-1}=\frac{0+2\sqrt{79}}{-2}
=\frac{2\sqrt{79}}{-2}
=\frac{\sqrt{79}}{-1}
$