Bài 1 .
a) A = 1 + \(\dfrac{1}{2+1}\) + \(\dfrac{1}{2^2+1}\) +\(\dfrac{1}{2^4+1}\) + .....+\(\dfrac{1}{2^{2n}+1}\)
b) B = \(\dfrac{1}{1.2.3}\) + \(\dfrac{1}{2.3.4}\) + \(\dfrac{1}{3.4.5}\) + ... + \(\dfrac{1}{\left(n-1\right).n.\left(n+1\right)}\)
c) C = \(\dfrac{1.2!}{2}\) + \(\dfrac{2.3!}{2^2}\) +... + \(\dfrac{n.\left(n+1\right)!}{2^n}\) (k! = 1. 2 . 3 ... k)