若2.5^x=1000,0.25^y=1000,则1/x-1/y=

若2.5^x=1000,0.25^y=1000,则1/x-1/y= 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 若x-y=1,求代数式x(x-y)+y(y-x)+2013的值 若x*x+y*y=x+y-1/2,求x,y的值如题 z=0.015x*x+y*x*0.05+(1-x-y)*2.5*(x+y) x>0.35.xy>0.70x+y 若2.5的x次方=1000,0.25的y次方=1000 则1/x-1/y=?什么 若实数x,y满足x-y+1》=0,x+y>=0,x 若变量x,y满足约束条件{x>=-1;y>=x;3x+2y 若实数x,y满足x-y+1>=0,x+y>=0,x 若(-x+6):(x-y):(4x+y)=3:14:1,求x+y 若(-x+6):(x-y):(4x+y)=3:14:1,求x+y 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|x+y-1|+（x-y-2)²=0,求代数式（x+2y)(x-2y）-（2x-y)(-y-2x)的值. 若x-y=1 化简（x+y)(x^2+y^2)(x^4+y^4)(x^8+y^8)(x^16+y^16) 若x+y=4,则多项式1/2(x+y)+4(x-y)-3（x-y）-3/2(x+y)-x+y值是（） y'/y=1/x 若(X×X+Y×Y)(X×X+Y×Y-5)=36,则X×X+Y×Y＝ 若x+y=1,x不等于0则x+(2xy+y^2)/x/(x+y)/x=