23=4x^2-13

Solution for 23=4x^2-13 equation:

23=4x^2-13

We move all terms to the left:

23-(4x^2-13)=0

We get rid of parentheses

-4x^2+13+23=0

We add all the numbers together, and all the variables

-4x^2+36=0

a = -4; b = 0; c = +36;
Δ = b2-4ac
Δ = 02-4·(-4)·36
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-24}{2*-4}=\frac{-24}{-8}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+24}{2*-4}=\frac{24}{-8}
=-3
$