HPT: \(\hept{\begin{cases}\frac{1}{x}+\frac{1}{y}=8\\x-y=12\end{cases}}\)
\(\Leftrightarrow\frac{1}{x}+\frac{1}{x-12}=8\)
\(\Leftrightarrow\frac{x-12+x-8x^2+96x}{x^2-12x}=0\)
\(\Leftrightarrow8x^2-98x+12=0\)
\(\Leftrightarrow4x^2-49x+6=0\)
\(\Leftrightarrow4\left(x-\frac{49}{8}\right)^2=\frac{2305}{16}\)
\(\Leftrightarrow x=\pm\frac{\sqrt{2305}+49}{8}\)'
\(\Leftrightarrow\orbr{\begin{cases}x=\frac{49+\sqrt{2305}}{8}\Leftrightarrow y=\frac{-47+\sqrt{2305}}{8}\\x=\frac{49-\sqrt{2305}}{8}\Leftrightarrow y=-\frac{47+\sqrt{2305}}{8}\end{cases}}\)
Kết luận nghiệm .....
p/s : nghiệm xấu quá đi :(((