784+x^2-80x=0

Solution for 784+x^2-80x=0 equation:

784+x^2-80x=0

a = 1; b = -80; c = +784;
Δ = b2-4ac
Δ = -802-4·1·784
Δ = 3264
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:

$\sqrt{\Delta}=\sqrt{3264}=\sqrt{64*51}=\sqrt{64}*\sqrt{51}=8\sqrt{51}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-80)-8\sqrt{51}}{2*1}=\frac{80-8\sqrt{51}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-80)+8\sqrt{51}}{2*1}=\frac{80+8\sqrt{51}}{2}
$