Depicting a function which looks like a geometric sequence

Question

I am to graph the following function: $f(x) = 1 + \frac{3x}{x^2 - 10} + (\frac{3x}{x^2 - 10})^2 + \dots $ I tried to use the formula for the sum of a geometric sequence, where: $a_0 = 1; m = \frac{3x}{x^2 - 10} $ And so the formula for the sum: $S = a_0\frac{1}{1 - m}$, which gives me $S = \frac{x^2 - 10}{x^2 - 3x - 10}$, but this form is really hard to plot. Can I do anything to simplify the formula, and so to graph it easier?