Ta có : \(\frac{3}{2.5}+\frac{3}{5.8}+\frac{3}{8.11}+......+\frac{3}{\left(x-3\right)x}\)
\(=\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+.....+\frac{1}{x-3}-\frac{1}{x}\)
\(=\frac{1}{2}-\frac{1}{x}\)
\(=\frac{x}{2x}-\frac{2}{2x}=\frac{x-2}{2x}\)
\(\frac{3}{2x5}\)+ \(\frac{3}{5x8}\)+ \(\frac{3}{8x11}\)+ ... + \(\frac{3}{\left(X-3\right)xX}\)= \(\frac{1}{6}\)
Giúp mk nhé!!!
\(\frac{1}{5x8}+\frac{1}{8x11}+...+\frac{1}{Xx\left(X+3\right)}=\frac{101}{1540}\)
Tính tổng
\(\frac{3^2}{2x5}+\frac{3^2}{5x8}\frac{3^2}{8x11}+......+\frac{3^2}{27x30}\)
Câu 1:Tìm a biết :
\(\frac{15,2x0,25-48,51:14,7}{a}\)=\(\frac{\left(\frac{13}{44}-\frac{2}{11}-\frac{5}{66}:2\frac{1}{2}\right)x1\frac{1}{5}}{3,2+0,8x\left(5\frac{1}{2}-3,25\right)}\)
Câu 2 :TÌM n
\(\frac{1}{2x5}\)+\(\frac{1}{5x8}\)+\(\frac{1}{8x11}\)+..........+\(\frac{1}{n\left(n+3\right)}\)=\(\frac{31}{198}\)
a)\(\frac{3}{5x8}+\frac{3}{8x11}+...+\frac{3}{2006x2009}\)
b)\(\frac{1}{6x10}+\frac{1}{10x14}+...+\frac{1}{402x406}\)
c)\(\frac{10}{7x12}+\frac{10}{12x17}+...+\frac{10}{502x507}\)
Ai làm nhanh nhất mk sẽ tick cho.Mk đag cần gấp.Mong các bn giúp đỡ
Tính:
\(A=\frac{6}{2x5}+\frac{6}{5x8}+\frac{6}{8x11}+...+\frac{6}{47x50}\)
\(3\left(x-\frac{1}{5}\right)-7\left(\frac{5}{14}-3\right)=20\)
\(\frac{2}{3}-\frac{1}{5}\left(x-\frac{1}{4}\right)=\frac{3}{2}-\frac{1}{4}\)
Giúp mình vs !!!!!!!@@@@@
Thanks trước nha
B = 3/2x5 + 3/5x8 + 3/8x11 + ... +3/26x29
