Find the exact value of the sum of n0 to infinity of n13nSol
Find the exact value of the sum of n=0 to infinity of (n+1)/(3^n)
Solution
n=0 xn+1 = x/(1-x)
Differentiate:
n=0 (n+1)xn = 1/(1-x)2
Therefore:
n=0 (n+1)(1/3)n = 1/(1-1/3)2 = 1/(4/9) = 9/4 = 2.25
