In this problem, u will derive a nifty result (with some pretty important applications further down the road). a) using integration by parts, show that for any integer n 1, xne-Z dx = b) using l'Hospitals rule, show that (Vou vill need multiple applications of l'Hospitals rule: your solution should demonstrate the first two steps, and the last step.) c) Show that d) Convince me that (Note that n! = n(n 1) 2 1 denotes factorial.)