5x^2+5=81

Solution for 5x^2+5=81 equation:

5x^2+5=81

We move all terms to the left:

5x^2+5-(81)=0

We add all the numbers together, and all the variables

5x^2-76=0

a = 5; b = 0; c = -76;
Δ = b2-4ac
Δ = 02-4·5·(-76)
Δ = 1520
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:

$\sqrt{\Delta}=\sqrt{1520}=\sqrt{16*95}=\sqrt{16}*\sqrt{95}=4\sqrt{95}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{95}}{2*5}=\frac{0-4\sqrt{95}}{10}
=-\frac{4\sqrt{95}}{10}
=-\frac{2\sqrt{95}}{5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{95}}{2*5}=\frac{0+4\sqrt{95}}{10}
=\frac{4\sqrt{95}}{10}
=\frac{2\sqrt{95}}{5}
$