\(a;343-4\times\left(x+1\right)=143\)
\(4\times\left(x+1\right)=343-143\)
\(4\times\left(x+1\right)=200\)
\(x+1=200:4\)
\(x+1=50\)
\(x=50-1=49\)
Mấy câu hỏi trẻ trâu thì tự tính nhé
\(\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{x.\left(x+3\right)}=\frac{101}{1540}\)
\(\Leftrightarrow\frac{1}{3}.\left(\frac{3}{5.8}+\frac{3}{8.11}+...+\frac{3}{x.\left(x+3\right)}\right)=\frac{101}{1540}\)
\(\Leftrightarrow\frac{1}{3}\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{101}{1540}\)
\(\Leftrightarrow\frac{1}{3}.\left(\frac{1}{5}-\frac{1}{x+3}\right)=\frac{101}{1540}\)
\(\Leftrightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{303}{1540}\)
\(\Leftrightarrow\frac{1}{x+3}=\frac{1}{308}\)
\(\Leftrightarrow x+3=308\)
\(\Leftrightarrow x=305\)
Vậy x=305
\(131+\left(26-3\times x\right):5=135\)
\(\left(26-3\times x\right):5=135-131\)
\(\left(26-3\times x\right):5=4\)
\(26-3\times x=4\times5\)
\(26-3\times x=20\)
\(3\times x=26-20\)
\(3\times x=6\)
\(x=6:3=2\)
\(4\times x+3=\frac{4321}{21}\)
\(4\times x=\frac{4321-63}{21}\)
\(4\times x=\frac{4258}{21}\)
\(x=\frac{4258}{21}:4=\frac{2129}{42}\)
\(\frac{1}{5\times8}+\frac{1}{8\times11}+...+\frac{1}{x\times\left(x+3\right)}=\frac{101}{1540}\)
\(\frac{1}{3}\left(\frac{3}{5\times8}+\frac{3}{8\times11}+...+\frac{3}{x\times\left(x+3\right)}\right)=\frac{101}{1540}\)
\(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{x}-\frac{1}{x+3}=\frac{101}{1540}:\frac{1}{3}\)
\(\frac{1}{5}-\frac{1}{x+3}=\frac{303}{1540}\)
\(\frac{x+3-5}{5\times\left(x+3\right)}=\frac{303}{1540}\)
\(\frac{x-2}{x+3}=\frac{303}{308}\)
Suy ra x=305
