- #1

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## Homework Statement

Ok, so I don't need help with this part, I just got stuck at the following step when attempting to find the interval of convergence:

## The Attempt at a Solution

I got here:

-4 < x^2 < 4

So, I need to solve this inequality. But can I? How can I take the square root of negative 4? And if this isn't possible to solve, what is the interval of convergence?