\(A=\frac{3}{2\cdot4}+\frac{3}{4\cdot6}+...+\frac{3}{48\cdot50}\)---> Mik nghĩ bn ghi nhầm :]
\(A=\frac{3}{2}\left[\frac{1}{2\cdot4}+\frac{1}{4\cdot6}+...+\frac{1}{48\cdot50}\right]\)
\(A=\frac{3}{2}\left[\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{48}-\frac{1}{50}\right]\)
\(A=\frac{3}{2}\left[\frac{1}{2}-\frac{1}{50}\right]=\frac{3}{2}\cdot\frac{12}{25}=\frac{18}{25}\)
Vậy A = 18/25
\(B=\frac{5}{1\cdot3}+\frac{5}{3\cdot5}+...+\frac{5}{49\cdot51}\)
\(B=\frac{5}{2}\left[\frac{1}{1\cdot3}+\frac{1}{3\cdot5}+...+\frac{1}{49\cdot51}\right]\)
\(B=\frac{5}{2}\left[\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{49}-\frac{1}{51}\right]\)
\(B=\frac{5}{2}\left[1-\frac{1}{51}\right]=\frac{5}{2}\cdot\frac{50}{51}=\frac{125}{51}\)
Mik ghi đúng mà
Huhu ai giúp mik với
Nhanh mik
Cảm ơn Luân nhìu nha. Đúng là mik viết sai thật
