Question

Tính

A= \(\dfrac{3^2}{8.11}\)+ \(\dfrac{3^2}{18.21}\)+ \(\dfrac{3^2}{14.17}\)+......+ \(\dfrac{3^2}{197.200}\)

B= \(\dfrac{1}{25.27}\)+ \(\dfrac{1}{27.29}\)+ \(\dfrac{1}{29.31}\)+....+ \(\dfrac{1}{73.75}\)

các bạn giải ra giúp mik nha ! Thanks

Answer 1

B=1/2. (2/25.27+2/27.29+2/29.31+....+2/73.75) B=1/2. (1/25-1/27+1/27-1/29+1/29-1/31+....+1/73-1/75) B=1/2. (1/25-1/75) B=1/2. 2/75 B=1/75

Answer 2

\(3A=\dfrac{3}{8.11}+\dfrac{3}{18.21}+..+\dfrac{3}{197.200}\)

Answer 3

xl bạn , mình gửi nhầm câu a =)

Answer 4

2B = \(\dfrac{2}{25.27}+\dfrac{2}{27.29}+...+\dfrac{2}{73.75}=\dfrac{1}{25}-\dfrac{1}{27}+\dfrac{1}{27}-\dfrac{1}{29}+...+\dfrac{1}{73}-\dfrac{1}{75}=\dfrac{1}{25}-\dfrac{1}{75}=\dfrac{3}{75}-\dfrac{1}{75}=\dfrac{2}{75}\)\(B=\dfrac{2}{75}:2=\dfrac{2}{75}.\dfrac{1}{2}=\dfrac{1}{75}\)