System of two equations with two unknowns - can't get rid of $xy$ The system is:
$x^2 + 2y^2 + 3xy = 12$
$y^2 - 3y = 4$
I try to turn $x^2 + 2y^2 + 3xy$ into $(x + y)^2 + y^2 + xy$ , but it's a dead end from here. Can anyone please help?

The system consists the two equations 
$x^2 + 2y^2 + 3xy = 12$ and (!) 
$y^2 - 3y = 4.$
From the second equation we get $y=-1, y=4.$  Then from the first equation we find $x.$
