x2+8x=64

Solution for x2+8x=64 equation:

x2+8x=64

We move all terms to the left:

x2+8x-(64)=0

We add all the numbers together, and all the variables

x^2+8x-64=0

a = 1; b = 8; c = -64;
Δ = b2-4ac
Δ = 82-4·1·(-64)
Δ = 320
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:

$\sqrt{\Delta}=\sqrt{320}=\sqrt{64*5}=\sqrt{64}*\sqrt{5}=8\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-8\sqrt{5}}{2*1}=\frac{-8-8\sqrt{5}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+8\sqrt{5}}{2*1}=\frac{-8+8\sqrt{5}}{2}
$