à có ai chơi ngọc rồng không cho mk 1 nick có ddeeej là được
\(A=\frac{3}{1\cdot2}+\frac{3}{2\cdot3}+...+\frac{3}{49\cdot50}\)
\(A=3\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+...+\frac{1}{49\cdot50}\right)\)
\(A=3\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{49}-\frac{1}{50}\right)\)
\(A=3\left(1-\frac{1}{50}\right)\)
\(A=3\cdot\frac{49}{50}=\frac{147}{50}\)
A = 3/1.2 + 3/2.3 + 3/3.4 + ... + 3/49.50
A=3/1-3/2+3/2-3/3+3/3-3/4+...+3/49-3/50
A=3/1-3/50
A= 147/50
a) A=\(\frac{3}{1.2}+\frac{3}{2.3}+..+\frac{3}{49.50}\)
\(=3.\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{49.50}\right)\)
\(=3.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{49}-\frac{1}{50}\right)\)
\(=3.\left(1-\frac{1}{50}\right)\)
\(=3.\frac{49}{50}\)
\(=\frac{147}{50}\)
Vậy A\(=\frac{147}{50}\)
Phần b tương tự
