Toán Lớp 9: Chia ra hộ mình ạ:
$\left \{ {{4x+3y=6} \atop {2x+y=4}} \right.$
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Toán Lớp 9: Chia ra hộ mình ạ:
$\left \{ {{4x+3y=6} \atop {2x+y=4}} \right.$
Comments ( 2 )
=> $\begin{cases}4x+3y=6\\ 2(2x+y)=2.4\end{cases}$
=> $\begin{cases}4x+3y=6\\4x+2y=8\end{cases}$
=> $\begin{cases}4x+3y-(4x+2y)=6-8\\4x+2y=8\end{cases}$
=> $\begin{cases}y=-2\\4x+(-4)=8\end{cases}$
=> $\begin{cases}y=-2\\4x=12\end{cases}$
=> $\begin{cases}y=-2\\x=3\end{cases}$
Vậy $\begin{cases}y=-2\\x=3\end{cases}$
=> $\begin{cases} x=\dfrac{-3}{4}y+\dfrac{3}{2}\\2x+y=4 \end{cases}$
= 2(-3/4y +2/3) + y =4
=> y = -2
=> x = -3/4 . (-2) + 3/2
=> x = 3/2 + 3/2
=> $\begin{cases} 4.3+3.(-2)=6\\2.3-2=4 \end{cases}$
=> $\begin{cases} 6=6\\4=4 \end{cases}$
=> x = 3 ; y = -2