How to solve this question? The given solution is not even a bit helpful!

$$\begin{gathered} 46. If \alpha , x are real number and \left|a\right| < 1, \left|x\right| < 1, then \\ 1 + (1 + \alpha )x + (1 +\alpha + {\alpha }^2)x^2 + .. ...\infty is equal to \\ \left(a\right)\frac{1}{\left(1-\alpha \right)\left(1-\alpha x\right)} \left(b\right)\frac{1}{\left(1-\alpha \right)\left(1-x\right)} \\ \left(c\right) \frac{1}{\left(1-x\right)\left(1-\alpha x\right)} \left(d\right)\frac{1}{\left(1+x\alpha \right)\left(1-\alpha \right)} \end{gathered}$$