Question

 

Hãy giúp mình bài toán tính nhanh này ạ

 

Answer 1

a: m=2; n=3

b; \(A=\dfrac{1}{3}+\dfrac{1}{6}+...+\dfrac{1}{55}\)

\(=2\left(\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{110}\right)\)

\(=2\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{10}-\dfrac{1}{11}\right)\)

=2*9/22=9/11