\(\frac{18-x}{5}+\frac{17-x}{6}=\frac{16-x}{7}+\frac{15-x}{8}\)
\(\Leftrightarrow\left(\frac{18-x}{5}+1\right)+\left(\frac{17-x}{6}+1\right)=\left(\frac{16-x}{7}+1\right)+\left(\frac{15-x}{8}+1\right)\)
\(\Leftrightarrow\left(\frac{18-x+5}{5}\right)+\left(\frac{17-x+6}{6}\right)=\left(\frac{16-x+7}{7}\right)+\left(\frac{15-x+8}{8}\right)\)
\(\Leftrightarrow\frac{23-x}{5}+\frac{23-x}{6}=\frac{23-x}{7}+\frac{23-x}{8}\)
\(\Leftrightarrow\frac{23-x}{5}+\frac{23-x}{6}-\frac{23-x}{7}-\frac{23-x}{8}=0\)
\(\Leftrightarrow\left(23-x\right).\left(\frac{1}{5}+\frac{1}{6}-\frac{1}{7}-\frac{1}{8}\right)=0\)
Vì \(\frac{1}{5}+\frac{1}{6}-\frac{1}{7}-\frac{1}{8}\ne0.\)
\(\Leftrightarrow23-x=0\)
\(\Leftrightarrow x=23-0\)
\(\Leftrightarrow x=23.\)
Vậy phương trình có tập hợp nghiệm là: \(S=\left\{23\right\}.\)
Chúc bạn học tốt!
