Odpowiedź:
[tex]\begin{cases}x-2y=8\\x+y=2\end{cases}\\\\\\\begin{cases}x=8+2y\\x+y=2\end{cases}\\\\\\8+2y+y=2\\\\3y=2-8\\\\3y=-6\ \ /:3\\\\y=-2\\\\\\x=8+2\cdot(-2)=8-4=4\\\\\\\begin{cases}x=4\\y=-2\end{cases}[/tex]
[tex]b)\\\\\begin{cases}y=-1\\4x+3y=1\end{cases}\\\\\\4x+3\cdot(-1)=1\\\\4x-3=1\\\\4x=1+3\\\\4x=4\ \ /:4\\\\x=1\\\\\\\begin{cases}x=1\\y=-1\end{cases}\\\\\\c)\\\\\begin{cases}x-4y=12\\2x+y=6\end{cases}\\\\\\\begin{cases}x=12+4y\\2x+y=6\end{cases}\\\\\\2(12+4y)+y=6\\\\24+8y+y=6\\\\9y=6-24\\\\9y=-18\ \ /:9\\\\y=-2\\\\\\x=12+4\cdot(-2)=12-8=4\\\\\\\begin{cases}x=4\\y=-2\end{cases}[/tex]
