Derivatives and Integrals of Power Series
As long as we are strictly inside the interval of convergence, we can take derivatives and integrals of power series term by term. Namely,
$$\frac{d}{dx}\left(\sum_{n=0}^\infty a_n \,x^n\right)=\sum_{n=1}^\infty n\,a_n \,x^{n-1}$$
$$
\int\left(\sum_{n=0}^\infty a_n \,x^n\right)\, dx = \left(\sum_{n=0}^\infty a_n \frac{x^{n+1}}{n+1}\right)+C$$
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The same holds for power series centered at $a$.
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