Help!!
For some real number \(a\) and some positive integer \(n\), the first few terms in the expansion of $(1 + ax)^n$ are \[1 - 20x + 150x^2 + cx^3 + \dotsb.\]
Find $c$.
+118 Use the Binomial Theorem. What does this expansion look like in terms of $a$ and $n$? Can you set up some equations based on the given coefficients (-20 and 150 for x and x^2 respectively)?
