Lời giải:
a.
HPT \(\Leftrightarrow \left\{\begin{matrix} 5x+10=2y+14\\ 3x+3y=17-x\end{matrix}\right.\Leftrightarrow \left\{\begin{matrix} 5x=2y+4\\ 4x=17-3y\end{matrix}\right.\)
\(\Leftrightarrow \left\{\begin{matrix} 20x=8y+16\\ 20x=85-15y\end{matrix}\right.\Rightarrow 8y+16=85-15y\Leftrightarrow y=3\)
\(x=\frac{17-3y}{4}=\frac{17-3.3}{4}=2\)
b.
HPT \(\Leftrightarrow \left\{\begin{matrix} 3x=3-y\\ 2x=y+7\end{matrix}\right.\Rightarrow 5x=10\Rightarrow x=2\)
$y=2x-7=2.2-7=-3$
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