Question

x-y+2=0
x+4=0
Вычтем из первого x-y+2=0
уравнения второе -
x+4=0
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??x+??y+??=0

Answer 1

$x-y+2=0\\x+4=0\\--------\\\\x-y+2-(x+4)=0-0\\\underline {x}-y+\underline {\underline {2}}-\underline {x}-\underline {\underline {4}}=0\\\\-y-2=0\; \; \; \Rightarrow \; \; \; y+2=0\; ,\; y=2$