Is that to the power of 3x or multiplied by 3x??
If it's multiplied by 3x than it's simple it'll be the lim as x tends to infinity of (x^2/x^2) * lim as x tends to infinity of 3x which will give you 1*infinity which is infinity. If it's raised to the power of 3x then you will transform it to e^(lim x->infinity 3xlog((x^2+x-1)/(x^2-x+1))). Now see what you can solve from that.