Question 121512
12-6y+y^2

well this involves imaginary numbers and if you don't know how to deal with them then there is no way to simplify this, otherwise its just the quadratic formula.

a = 1
b = -6
c = 12

{{{y = (-b +- sqrt(b^2-(4*a*c)))/(2*a)}}}
{{{y = (6 +- sqrt((-6)^2-(4*1*12)))/(2)}}}
{{{y = (6 +- sqrt(36-(4*12)))/(2)}}}
{{{y = (6 +- sqrt(36-48))/(2)}}}
{{{y = (6 +- sqrt(-12))/(2)}}}
{{{y = (6 +- 2*sqrt(3)i)/(2)}}}
{{{y = 3 +- sqrt(3)i}}}