3x^2-5=75

Solution for 3x^2-5=75 equation:

3x^2-5=75

We move all terms to the left:

3x^2-5-(75)=0

We add all the numbers together, and all the variables

3x^2-80=0

a = 3; b = 0; c = -80;
Δ = b2-4ac
Δ = 02-4·3·(-80)
Δ = 960
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:

$\sqrt{\Delta}=\sqrt{960}=\sqrt{64*15}=\sqrt{64}*\sqrt{15}=8\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-8\sqrt{15}}{2*3}=\frac{0-8\sqrt{15}}{6}
=-\frac{8\sqrt{15}}{6}
=-\frac{4\sqrt{15}}{3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+8\sqrt{15}}{2*3}=\frac{0+8\sqrt{15}}{6}
=\frac{8\sqrt{15}}{6}
=\frac{4\sqrt{15}}{3}
$