已知X,Y都是正数,求证:(x+y)(x^2+y^2)(x^3+y^3)≥8x^3y^3
已知x,y,z都是正数,且xyz=1,求证:x^2/(y+z)+y^2/(x+z)+z^2/(x+y)≥3/2
已知xy都是正数,若x+2y=3,求1/x+2/y最小值
已知x,y,z都是正数,且3^x=4^y=6^z 求证 1/z-1/x=1/2y
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)
[(3x+y)(x-y)-(2x+3y)(x-y)]*(x-y)
化简:(x-3y)(x+y)-(x-2y)(x+2y)-(x-y)平方
【x-3y][x+y]-[x-2y][x +2y]-[x-y
有这样一道题:"计算(2*x*x*x-3*x*x*y-2*x*y*y)-(x*x*x-2*x*y*y+y*y*y)+【-
设x,y都是正数,且1/x+2/y=3,求2x+y的最小值
已知:3x=8y.求(1)x+y/y (2)2x+3y/x-2y
【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2=