11: There is a factorial of k in the denominator, which clearly points to the exponential expansion. There is only one problem, the term k + 1 in the numerator.

The usual way of handling such a situation is to also create k + 1 in the denominator by integrating x^k, which is something that we already have there. We see that the procedure will involve integration, which is usually handled more easily if you first denote the sum of the given series as f (x) and then manipulate simultaneously both sides of this equality.

There is an alternative way to work with the k + 1 in the numerator. Try to think of some way to achieve cancelling with the factorial.

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