1. The problem statement, all variables and given/known data http://img87.imageshack.us/img87/469/17317851uu7.jpg [Broken] 2. Relevant equations 3. The attempt at a solution First I have to show that P(1) is true |a1| ≤ |a1| This is true Assume above is true for all n. Show that |∑i=1n+1 ai| ≤ n+1∑i=1 |ai| |a1 + a2 + a3…+ an + an+1| ≤ |a1| + |a2| + |a3| +…+ |an| + |an+1| |∑i=1n ai + an+1| ≤ n+1∑i=1 |ai| + |an+1| assuming I'm on the right track. How can i proceed. This problem is so abstract its driving me crazy. Sorry for formatting.