x2-12x=39

Solution for x2-12x=39 equation:

x2-12x=39

We move all terms to the left:

x2-12x-(39)=0

We add all the numbers together, and all the variables

x^2-12x-39=0

a = 1; b = -12; c = -39;
Δ = b2-4ac
Δ = -122-4·1·(-39)
Δ = 300
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:

$\sqrt{\Delta}=\sqrt{300}=\sqrt{100*3}=\sqrt{100}*\sqrt{3}=10\sqrt{3}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-10\sqrt{3}}{2*1}=\frac{12-10\sqrt{3}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+10\sqrt{3}}{2*1}=\frac{12+10\sqrt{3}}{2}
$