Toán Lớp 7: 4x= -11y và x mũ 2 – 3y mũ 2 =803
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Toán Lớp 7: 4x= -11y và x mũ 2 – 3y mũ 2 =803
Comments ( 1 )
4x = – 11y\\
\Leftrightarrow \dfrac{x}{{ – 11}} = \dfrac{y}{4} = k \Leftrightarrow \left\{ \begin{array}{l}
x = – 11k\\
y = 4k
\end{array} \right.\\
Khi:{x^2} – 3{y^2} = 803\\
\Leftrightarrow {\left( { – 11k} \right)^2} – 3{\left( {4k} \right)^2} = 803\\
\Leftrightarrow 121{k^2} – 48{k^2} = 803\\
\Leftrightarrow 73{k^2} = 803\\
\Leftrightarrow {k^2} = 11\\
\Leftrightarrow \left[ \begin{array}{l}
k = \sqrt {11} \Leftrightarrow x = – 11\sqrt {11} ;y = 4\sqrt {11} \\
k = – \sqrt {11} \Leftrightarrow x = 11\sqrt {11} ;y = – 4\sqrt {11}
\end{array} \right.\\
Vậy\,\left( {x;y} \right) = \left\{ {\left( { – 11\sqrt {11} ;4\sqrt {11} } \right);\left( {11\sqrt {11} ; – 4\sqrt {11} } \right)} \right\}
\end{array}$