1)3x-2y=12
x+2y=-4
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4x=8, x=2
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x=2, 2y=3x-12, 2y=6-12, 2y=-6, y=-3
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/x,y/=2,-3/
2)3x-y=4
2x+3y=10
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y=3x-4
2x+3y=10
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y=3x-4
2x+3(3x-4)=10
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y=3x-4
2x+9x-12=10
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y=3x-4
11x=22, x=2
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y=6-4, y=2
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/x,y/=/2,2/
3)2x-y=3
6x-3y=9 /:3
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2x-y=3
2x-y=3
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y=2x-3
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/x , 2x-3/ , x∈R