3(5x^2-5)=60

Solution for 3(5x^2-5)=60 equation:

3(5x^2-5)=60

We move all terms to the left:

3(5x^2-5)-(60)=0

We multiply parentheses

15x^2-15-60=0

We add all the numbers together, and all the variables

15x^2-75=0

a = 15; b = 0; c = -75;
Δ = b2-4ac
Δ = 02-4·15·(-75)
Δ = 4500
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:

$\sqrt{\Delta}=\sqrt{4500}=\sqrt{900*5}=\sqrt{900}*\sqrt{5}=30\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-30\sqrt{5}}{2*15}=\frac{0-30\sqrt{5}}{30}
=-\frac{30\sqrt{5}}{30}
=-\sqrt{5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+30\sqrt{5}}{2*15}=\frac{0+30\sqrt{5}}{30}
=\frac{30\sqrt{5}}{30}
=\sqrt{5}
$