What is the answer? im trying to figure it out and its hurting my head

Umm.. just started this 2day and its not on my notes(p′︵‵。)

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

Louis wants to carpet the rectangular floor of his basement the basement has an area of 864 square feet the width of the basement is 2/3 its length what is the length of lewis's basement