x2=72+15

Solution for x2=72+15 equation:

x2=72+15

We move all terms to the left:

x2-(72+15)=0

We add all the numbers together, and all the variables

x2-87=0

We add all the numbers together, and all the variables

x^2-87=0

a = 1; b = 0; c = -87;
Δ = b2-4ac
Δ = 02-4·1·(-87)
Δ = 348
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:

$\sqrt{\Delta}=\sqrt{348}=\sqrt{4*87}=\sqrt{4}*\sqrt{87}=2\sqrt{87}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{87}}{2*1}=\frac{0-2\sqrt{87}}{2}
=-\frac{2\sqrt{87}}{2}
=-\sqrt{87}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{87}}{2*1}=\frac{0+2\sqrt{87}}{2}
=\frac{2\sqrt{87}}{2}
=\sqrt{87}
$