Please help I don't understand

Proceed as in example 3 in section 6.1 to rewrite the given expression using a single power series whose general term involves xk. ∞ n(n − 1)cnxn − 2 n = 2 − 4 ∞ ncnxn n = 1 + ∞ cnxn n = 0

Maci and i are making a small kite. two sides are 10". two sides are 5". the shorter diagonal is 6". round all your answers to the nearest tenth. 1. what is the distance from the peak of the kite to the intersection of the diagonals? 2. what is the distance from intersection of the diagonals to the top of the tail? 3. what is the length of the longer diagonal?

The sum of five and a number n is at least 12