X^2-14x=28

Solution for X^2-14x=28 equation:

X^2-14X=28

We move all terms to the left:

X^2-14X-(28)=0

a = 1; b = -14; c = -28;
Δ = b2-4ac
Δ = -142-4·1·(-28)
Δ = 308
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:

$\sqrt{\Delta}=\sqrt{308}=\sqrt{4*77}=\sqrt{4}*\sqrt{77}=2\sqrt{77}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-2\sqrt{77}}{2*1}=\frac{14-2\sqrt{77}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+2\sqrt{77}}{2*1}=\frac{14+2\sqrt{77}}{2}
$