5(x^2-1)=135

Solution for 5(x^2-1)=135 equation:

5(x^2-1)=135

We move all terms to the left:

5(x^2-1)-(135)=0

We multiply parentheses

5x^2-5-135=0

We add all the numbers together, and all the variables

5x^2-140=0

a = 5; b = 0; c = -140;
Δ = b2-4ac
Δ = 02-4·5·(-140)
Δ = 2800
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:

$\sqrt{\Delta}=\sqrt{2800}=\sqrt{400*7}=\sqrt{400}*\sqrt{7}=20\sqrt{7}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-20\sqrt{7}}{2*5}=\frac{0-20\sqrt{7}}{10}
=-\frac{20\sqrt{7}}{10}
=-2\sqrt{7}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+20\sqrt{7}}{2*5}=\frac{0+20\sqrt{7}}{10}
=\frac{20\sqrt{7}}{10}
=2\sqrt{7}
$