{X+2Y=145{2X+3Y=280
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{X+2Y=145
{2X+3Y=280
{2X+3Y=280
![{X+2Y=145{2X+3Y=280](/uploads/image/z/19941300-36-0.jpg?t=%EF%BD%9BX%2B2Y%3D145%EF%BD%9B2X%2B3Y%3D280)
2X+4Y=290
左边减左边,右边减右边
2X+4Y-2X-3Y=290-280
Y=10
X=125
左边减左边,右边减右边
2X+4Y-2X-3Y=290-280
Y=10
X=125
已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2=
先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2
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
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于