Question

tính :S= 1/3 + 1/9 + 1/27 + 1/135 + 1/405

Answer 1

S = 1/3 + 1/9 +1/27 + 1/135 + 1/405

S = 135/405 + 45/405 + 15/405 + 3/405 + 1/405

S = \(\frac{135+45+15+3+1}{405}\)

S = \(\frac{199}{405}\)

Answer 2

199/405