若1/x+4/y=1,(x>0,y>0),则xy的最小值是?

证明：若x>0,y>0,x+y=1,则（x+1/x)(y+1/y)≥25/4 若x,y满足约束条件,x>=0,y>=0,x-y>=-1,3x+4y 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 已知4x+6y=1 若x=y 则x,y的值等于?若x+y=0 则x=?y=? 若实数x,y满足x-y+1》=0,x+y>=0,x 若实数x,y满足x-y+1>=0,x+y>=0,x 若实数X,Y满足X²+Y²+4X-2Y +1=0,则X²-6X+Y²-2Y的最大值是多少 X>0 Y>0证1/x+1/y>=4/(x+y)X>0 Y>0 证1/x+1/y>=4/(x+y) x>0 y>0 x+y=1,4/X+9/y最小值x>0 y>0 x+y=1,求4/X+9/y最小值 若|x+y-1|+（x-y-2)²=0,求代数式（x+2y)(x-2y）-（2x-y)(-y-2x)的值. {4x-3y-10=0 3x-2y=0,{3x-4(x-y)=2 2x-3y=1,{2(x+y)-(x-y)=3 (x+y)-2(x-y)=1 若x^5+x^4y+x^4+x+y+1=0,且3x+2y=1,求x,y的值 {x+y=1 ,xy=-6{x(2x-3)=0,y=x²-1{(3x+4y-3)(3x+4y+3)=0,3x+2y=5{(x-y+2)(x+y)=0,x²+y²=8{(x+y)((x+y-1)=0,(x-y)(x-y-1)=0 若x+y=1,x不等于0则x+(2xy+y^2)/x/(x+y)/x= 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 4x+y-9>=0 ,x-y-1 若x²-4xy+5y²-2y+1=0,求x,y 如果|x-y+1|+y^2-4y+4=0,求出x,y的值