求解(1){2x-y=9 3x+y=7 (2)｛4x-3y=5.6 5x+3y=7.4 (3)｛2x+3y+19=0 x

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求解(1){2x-y=9 3x+y=7 (2)｛4x-3y=5.6 5x+3y=7.4 (3)｛2x+3y+19=0 x+5y-1=0
(4)｛x+y/2+x-y=1 4（x+y)-5(x-y)=2

(1)2x-y+(3x+y)=9+7 5x=16 x=16/5
把x=16/5代入2x-y=9中
32/5-y=9 y=13/5
(2)4x-3y+(5x+3y)=5.6+7.4 9x=15 X=15/9
把x=15/9代入4x-3y=5.6中
y=96/270
(3)(X+5Y-1=0)*2 即2X+10Y=2
2x+3y+19-(2x+10y-2)=-21 y=3
把y=3代入2x+3y+19=0
x=-2/5
(4)化简{2x-y/2=1 -x+9y=2
(-x+9y=2)*2 -2x+18y=4
-2x+18y+(2x-y/2)=5 y=2/7
把y=2/7代入-x+9y=2
x=4/7

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