X2-12x+3=15

Solution for X2-12x+3=15 equation:

X2-12X+3=15

We move all terms to the left:

X2-12X+3-(15)=0

We add all the numbers together, and all the variables

X^2-12X-12=0

a = 1; b = -12; c = -12;
Δ = b2-4ac
Δ = -122-4·1·(-12)
Δ = 192
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:

$\sqrt{\Delta}=\sqrt{192}=\sqrt{64*3}=\sqrt{64}*\sqrt{3}=8\sqrt{3}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-8\sqrt{3}}{2*1}=\frac{12-8\sqrt{3}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+8\sqrt{3}}{2*1}=\frac{12+8\sqrt{3}}{2}
$