若x+2y=1 2x-3y=-1,则2x+4y-2/3 + 6x-9y/2=
{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
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
若2x-3y+4=0则x(x*x-1)+x(5-x*x)-6y+7
9y=3x-(x-1),4(x+y)-(2x+4)=8y
若x=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值?
若全集I={(x,y)|x,y∈R},集合M={(x,y)|(y-3)/(x-2)},N{(x,y)|y=x=1},则(
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2
已知4x=9y求(1)x+y/y (2)y-x/2x
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