\(\left\{{}\begin{matrix}2x-\left(m^2+m+1\right)y=-m^2-9\left(1\right)\\m^4x+\left(2m^2+1\right)y=1\left(2\right)\end{matrix}\right.\)
rút x từ (1) thế vào (2)
\(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{\left(m^2+m+1\right)y-m^2-9}{2}\left(3\right)\\m^4\left[\dfrac{\left(m^2+m+1\right)y-m^2-9}{2}\right]+\left(2m^2+1\right)y=1\left(4\right)\end{matrix}\right.\)
\(\left(4\right)\Leftrightarrow m^4\left(m^2+m+1\right)y-m^4\left(m^2+9\right)+2\left(2m^2+1\right)y=2\)
\(\Leftrightarrow\left[m^4\left(m^2+m+1\right)+4m^2+2\right]y=m^4\left(m^2+9\right)+2\)
\(\Leftrightarrow Ay=B\)
Taco
\(\left\{{}\begin{matrix}m^2+m+1=\left(m+\dfrac{1}{2}\right)^2+\dfrac{3}{4}>0\forall m\in R\\4m^2+2>0\forall m\in R\\m^4\left(m^2+9\right)>0\forall m\in R\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}A>0\forall m\in R\\B>0\forall m\in R\end{matrix}\right.\)
\(\Rightarrow y>0\forall m\in R\)
Kết luận không có m thủa mãn
