Question 856185
{{{6*x=(x^2 + 6) + (x^2 + 12)}}}

{{{6*x=2x^2 + 18}}}
{{{2x^2-6x+18=0}}}
{{{x^2-3x+9=0}}}
Use the quadratic formula,
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
{{{x = (-(-3) +- sqrt( (-3)^2-4*1*9 ))/(2*1) }}} 
{{{x = (3 +- sqrt( 9-36 ))/(2) }}}
{{{x = (3 +- sqrt( -27 ))/(2) }}}
{{{x = (3+- 3*sqrt(3)i )/(2) }}}