I'm self-teaching geometric progressions and was asked to find the sum to $n$ terms of $x + 1 + \frac{1}{x} + \cdots$ so I used the formula $\frac{a(r^n - 1)}{r - 1}$ with $a = x$ and $r = \frac{1}{x}$, and I arrived at $\frac{x^{1-n} - x}{x^{-1} - 1}$ The answer in the book is $\frac{x^n-1}{x^{n-2}(x - 1)}$
I cannot see how to manipulate my answer to get to the one in the book (though I know they're equivalent as Wolfram Alpha says so). Hope someone can show me how to approach this?