2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②
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2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②2
2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②
2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②
2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②
2(x+y)-3(X-y)=3 ① 4(X+y)+3(x-y)=15②
①+②得,
6(x+y)=18
x+y=6 ③
则x-y=[2(x+y)-3]/3=3 ④
③+④得,
2x=9
所以
x=9/2
y=6-x=3/2
{2(x+y)-3(x-y)=3,
4(x+y)+3x=15+3y
所以
{2(x+y)-3(x-y)=3,
4(x+y)+3（x-y)=15
相加得
6（x+y）=18
x+y=3
所以
3(x-y)=15-4×3
x-y=1
从而
x=2
y=1
(x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)=
2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15
x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20
{(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20
4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6
3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2
（x+y）/2- x-y/2=6 3(x+y)=4(x-y)
x+y/3+x-y/2=6 4(x+y)-2(x-y)=40
4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
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2(x+y)-3(X-y)=3①4(X+y)+3(x-y)=15②
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