A= 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6
A= 1/2 - 1/3+ 1/3-1/4 + 1/4-1/5+ 1/5-1/6
A= 1/2- 1/6
A= 1/3
\(A=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\)
\(\Rightarrow A=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(\Rightarrow A=\frac{1}{2}-\frac{1}{6}\)
\(\Rightarrow A=\frac{1}{3}\)
Wa cảm ơn các bạn nhiều nha
