What you have written is NOT a sequence, but a function of one variable. If you are asking how to find the limit of that function, as x approaches perhaps infinity, or perhaps even some specific point like x==-1, then a limit is required. In mathematics, you may have learned to use tools like the l'hospital rule.
In MATLAB, you would just use the function limit, in the symbolic toolbox. (I'also have posted a limest tool on the file exchange. The symbolic toolbox function is more powerful of course.)
I won't solve your specific problem, since this is probably homework. However, you can do this, on a similar problem:
syms x
limit((x^2 + 1)/(3 - 2*x + 4*x^2),inf)
