Limit x->infinity (sqrt 9x^2 + x -3x)
\(\displaystyle\lim_{ x\rightarrow \infty}(\sqrt 9x^2 + x -3x)\\ =\displaystyle\lim_{ x\rightarrow \infty}(3x^2 -2x)\\ =\displaystyle\lim_{ x\rightarrow \infty}(3x^2 -2x)\\ =\infty\)
Here is the graph, (y=3x^2-2x)you can see that as x grows larger so does y.