x^2-12x+14=21

Solution for x^2-12x+14=21 equation:

x^2-12x+14=21

We move all terms to the left:

x^2-12x+14-(21)=0

We add all the numbers together, and all the variables

x^2-12x-7=0

a = 1; b = -12; c = -7;
Δ = b2-4ac
Δ = -122-4·1·(-7)
Δ = 172
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:

$\sqrt{\Delta}=\sqrt{172}=\sqrt{4*43}=\sqrt{4}*\sqrt{43}=2\sqrt{43}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-2\sqrt{43}}{2*1}=\frac{12-2\sqrt{43}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+2\sqrt{43}}{2*1}=\frac{12+2\sqrt{43}}{2}
$