This expression is an expansion of the binomial expression \( \left( \frac{(1 + x)}{(n + 1)} \right)' \), where the right-hand side represents the binomial expansion of the series for \( (1 + x)^{n+1} \).
Each coefficient \( n_k \) corresponds to the binomial coefficient in the expansion. As we expand \( \left( \frac{(1 + x)}{(n + 1)} \right) \), the result includes terms like:
- The first term \( n_0 x \) is simply \( x \).
- The second term is \( n_1 \frac{x^2}{2} \), which is \( \frac{x^2}{2} \), and so on.
The general term in this expansion is \( n_k \frac{x^k}{k+1} \), where \( n_k \) are binomial coefficients.
This expansion allows us to approximate the behavior of \( \left( 1 + x \right)^{n+1} \) for small values of \( x \).