\(A=\dfrac{1}{2\cdot5}+\dfrac{1}{5\cdot8}+...+\dfrac{1}{95\cdot98}\)
\(3A=\dfrac{3}{2\cdot5}+\dfrac{3}{5\cdot8}+...+\dfrac{3}{95\cdot98}\)
\(3A=\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+...+\dfrac{1}{95}-\dfrac{1}{98}\)
\(3A=\dfrac{1}{2}-\dfrac{1}{98}\)
\(A=\dfrac{\dfrac{1}{2}-\dfrac{1}{98}}{3}=\dfrac{8}{49}\)
\(\dfrac{1}{2.5}+\dfrac{1}{5.8}+\dfrac{1}{8.11}+...+\dfrac{1}{92.95}+\dfrac{1}{95.98}\)
Rút gọn biểu thức 2.5+5.8+8.11+...+92.95+95.98
Tính A
A = 1/1.5 + 1/5.8 + 1/8.11 + ... + 1/98.101
\(A=\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{\left(3n-1\right)\left(3n+2\right)}\)
Tìm x biết: (1/2.5+1/5.8+1/8.11+...+1/65.68)x-7/34=19/68
tìm x biết
a 1/5.8+1/8.11+1/11.14+...1/x(x+3)=101/1540
b 1+1/3+1/6+1/10+...1/x(x+1)=\(1\frac{1991}{1993}\)
TÍNH
\(1-\frac{1}{2.5}-\frac{1}{5.8}-\frac{1}{8.11}-...-\frac{1}{92.95}\)
Rút gọn A= \(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}....+\frac{1}{\left(3n+2\right)\left(3n+5\right)}\)
TIM X
\(\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.13}+....+\frac{1}{x\left(x+3\right)}\)
