\(\left\{{}\begin{matrix}9x^2-3y=15\\2x^2+3y=18\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}11x^2=33\\y=3x^2-5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x^2=3\\y=3x^2-5\end{matrix}\right.\)
\(\Leftrightarrow x=\pm\sqrt{3}\)
Với x = căn3 => y = 3.3 - 5 = 4
Với x = -căn3 => y = 3.3 - 5 = 4
\(\Leftrightarrow\left\{{}\begin{matrix}9x^2-3y=15\\2x^2+3y=18\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}11x^2=33\\2x^2+3y=18\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x^2=3\\2x^2+3y=18\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=\pm\sqrt{3}\\2.3+3y=18\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=\pm\sqrt{3}\\y=4\end{matrix}\right.\)
