Question

Mọi người giúp mình giải hệ phương trình này bằng một cách dễ hiểu nhất với!Cảm ơn!

\(\begin{cases} \dfrac{5}{y}-\dfrac{7}{y}=9\\ \dfrac{4}{x}-\dfrac{9}{y}=35 \end{cases} \)

Answer 1

\(\left\{{}\begin{matrix}\dfrac{5}{y}-\dfrac{7}{y}=9\\\dfrac{4}{x}-\dfrac{9}{y}=35\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{-2}{y}=9\\\dfrac{4}{x}-\dfrac{9}{y}=35\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{2}{9}\\\dfrac{4}{x}-\dfrac{9}{-\dfrac{2}{9}}=35\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{2}{9}\\\dfrac{4}{x}=-\dfrac{11}{2}\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{2}{9}\\x=-\dfrac{8}{11}\end{matrix}\right.\)

Vậy....

Answer 2

8 \ 11

Answer 3

Ta có: \(\left\{{}\begin{matrix}\dfrac{5}{x}-\dfrac{7}{y}=9\\\dfrac{4}{x}-\dfrac{9}{y}=35\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{20}{x}-\dfrac{28}{y}=36\\\dfrac{20}{x}-\dfrac{45}{y}=175\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{17}{y}=-139\\\dfrac{4}{x}-\dfrac{9}{y}=35\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{-17}{139}\\\dfrac{4}{x}=-\dfrac{656}{17}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=-\dfrac{17}{139}\\x=-\dfrac{17}{164}\end{matrix}\right.\)