{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
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{3(x+y)-4(x-y)=4{x+y/2+x-y/6=1{3(x+y)-4(x-y)=4{x+y/2+x-y/6=1{3(x+y)-4(x-y)=4{x+y/2+x-y/6=13(x+y)-4(x
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
3(x+y)-4(x-y)=4
(x+y)/2+(x-y)/6=1
令a=x+y,b=x-y
3a-4b=4 (1)
a/2+b/6=1
则3a+b=6 (2)
(2)-(1)
5b=2
b=2/5
a=(6-b)/3=28/15
x+y=28/15
x-y=2/5
相加
2x=34/15
x=17/15
y=28/15-x=11/15
(x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)=
（y-x)+x(x-y)^3-(y-x)^4 因式分解
（3x-y)(y+3x)-(4x-3y)（4x+3y)=?
（5x+3y)(3y-5x)-(4x-y)(4y+x)=
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1
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
x(x-3y)=4y(x-3y),求x:y
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
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
x/3=y/4,求(x*x-xy)/(x*x+y*y)的值