Odpowiedź:
[tex]a)\\\\\begin{cases}2x+y=4\\x+\frac{1}{2}y=2\end{cases}\\\\\\\begin{cases}y=4-2x\\x+\frac{1}{2}y=2\end{cases}\\\\\\x+\frac{1}{2}(4-2x)=2\\\\x+2-x=2\\\\2=2\\\\Uklad\ \ r\'owna\'n\ \ nieoznaczony(ma\ \ niesko\'nczenie\ \ wiele\ \ rozwiaza\'n)[/tex]
[tex]b)\\\\\begin{cases}2x+4y=-7\ \ /:2\\7x-3y=1\end{cases}\\\\\\\begin{cases}x+2y=-\frac{7}{2}\\7x-3y=1\end{cases}\\\\\\\begin{cases}x=-\frac{7}{2}-2y\\7x-3y=1\end{cases}\\\\\\7(-\frac{7}{2}-2y)-3y=1\\\\-\frac{49}{2}-14y-3y=1\\\\-17y=1+\frac{49}{2}\\\\-17y=\frac{2}{2}+\frac{49}{2}\\\\-17y=\frac{51}{2}\ \ /:(-17)\\\\y=-\frac{\not51^3}{2}\cdot\frac{1}{\not17_{1}}\\\\y=-\frac{3}{2}[/tex]
[tex]x=-\frac{7}{2}-2\cdot(-\frac{3}{2})=-\frac{7}{2}+\not2\cdot\frac{3}{\not2}=-\frac{7}{2}+3=- \frac{7}{2}+\frac{6}{2}=-\frac{1}{2}\\\\\begin{cases}x=-\frac{1}{2}\\y=-\frac{3}{2}\end{cases}[/tex]
