# The Closed Form Still Exists!

**Calculus**Level 2

We know that the geometric progression sum of

\[ 1 - x + x^2 - x^3 + x^4 - \cdots \]

can be written as \( \dfrac1{1+x} \), where \(-1<x<1\).

If we integrate each of these terms with respect to \(x\), we get the series below. Which of the following is equivalent to the series below?

\[ x -\dfrac12 x^2 + \dfrac13x^3 - \dfrac14 x^4 + \dfrac15x^5 - \cdots \]

Assume we ignore the arbitrary constant of integration.