Miike012 said:I highlighted the portion in red in the paint document that I'm not understanding.
How can we see by inspection that the product is equal to the series 2?
The second line in the paint document is equal to n/xn(1 + (2n-1)x + (2n-1)(2n-1)/2!x2 + ...) by using the binomial theorempasmith said:The term independent of x in the product is equal to the series (2); this is because the term independent of x is a sum of terms of the form kc_k x^k \times c_k/x^k = kc_k^2.