x(x-1)(x+1)=720

Solution for x(x-1)(x+1)=720 equation:

x(x-1)(x+1)=720

We move all terms to the left:

x(x-1)(x+1)-(720)=0

We use the square of the difference formula

x^2-1-720=0

We add all the numbers together, and all the variables

x^2-721=0

a = 1; b = 0; c = -721;
Δ = b2-4ac
Δ = 02-4·1·(-721)
Δ = 2884
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:

$\sqrt{\Delta}=\sqrt{2884}=\sqrt{4*721}=\sqrt{4}*\sqrt{721}=2\sqrt{721}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{721}}{2*1}=\frac{0-2\sqrt{721}}{2}
=-\frac{2\sqrt{721}}{2}
=-\sqrt{721}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{721}}{2*1}=\frac{0+2\sqrt{721}}{2}
=\frac{2\sqrt{721}}{2}
=\sqrt{721}
$