Question

Tìm x :

a) \(\frac{1}{5.8}+\frac{1}{8.11}+.....+\frac{1}{x\left(x+3\right)}=\frac{101}{1540}\)

b) 1 + \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+.....+\frac{1}{x\left(x+1\right):2}=1\frac{1991}{1993}\)

Ai lm đúng và đủ cho 3 like nha !

Answer 1

Bấm vào câu hỏi nha , mk có sửa chút !

Answer 2

a)\(\frac{1}{5.8}+\frac{1}{8.11}+.....+\frac{1}{x\left(x+3\right)}=\frac{101}{1540}\)

\(\frac{3}{5.8}+\frac{3}{8.11}+...+\frac{3}{x\left(x+3\right)}=\frac{101}{1540}\)

\(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-...-\frac{1}{x+3}=\frac{101}{1540}\)

\(\frac{1}{5}-\frac{1}{x+3}=\frac{101}{1540}\Rightarrow\frac{1}{x+3}=\frac{1}{5}-\frac{101}{1540}=\frac{207}{1540}\)

\(\frac{1}{x+3}=\frac{207}{1540}\Leftrightarrow207\left(x+3\right)=1540\)

\(207x+621=1540\)

\(207x=1540-621=919\Rightarrow x=\frac{919}{207}\)

Answer 3

a) x=305

b) x=1992