x+2y+2=25 4x+y=74
x,y属于R*,且x+y=1,求证:(1)(x+1/x)(y+1/y)≥25/4 (2)(x+1/x)^2+(y+1/y
已知x.x+y.y+8x+6y+25=0,求代数式(x.x-4y.y)/(x.x+4xy+4y.y)-x/(x+2y)的
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
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
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6
已知4x=9y求(1)x+y/y (2)y-x/2x
(x+y)(x+2y)(x+3y)(x+4y)=-40
已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值?
2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y
已知2x-y=10,求[(x²+y²)-(x-y)²+2y(x-y)]/4y