Question 171175
S=1/5+1/5^2+1/5^3+...+1/5^n
(1/5)S=1/5^2+1/5^3+...+1/5^n+1/5^(n+1)

S-(1/5)S = (4/5)S = 1/5 - (1/5)^(n+1)

S=1/4 - (5/4)(1/5)^(n+1)= 1/4(1-(1/5)^n)

i think you typed a 9 instead of a (