Answer
See below.
Work Step by Step
An infinite geometric series has a sum if and only if $|r|\lt1$, where $r$ is the common ratio. If it exists, then it equals $\frac{a_1}{1-r}$ where $a_1$ is the first term.
Here $|0.25x|\lt1\\-1\lt 0.25x\lt 1\\-4\lt x\lt 4$.
Hence the sum: $\dfrac{6}{1-0.25x}$
