x>0,y>0 2x+5y=20 1/x+1/y的最大值

x>0,y>0 2x+5y=20 1/x+1/y的最大值 （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x x*x+2x+y*y-4y+5=0 x= y= {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*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 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 设x大于1,y大于0,x^y+x^-y=2根号二,x^y-x^-y等于? mathematica软件,已知y[x],Y=f1(x),X(x)=f2(x),如何plot Y[X]?y[x_] := x + 9.81/2*x*xk=1X[x] = x - k*y'[x]/(1 + (y'[x])^2)^0.5Y[x] = y[x] + k/(1 + (y'[x])^2)^0.5Plot[{y[x],Y[X],},{x,0,2}] x^2-x+y^2+2y+5/4=0 求x^-1+y^0 已知x>0,y>0,2/x+5/y=1,求x+y最小值 |x-2y+1|+(x+y-5)²=0,则5x+4y= 3x+4y-5=0 x^2+y^2=1求x.y 如果|x-2y+1|+|2x-y-5|=0,则x+y=? 如果|x-2y+1|+|x+y-5|=0,那么x= ,y= 如果|x-2y+1|+|2x-y-5|=0 .x+y等于几 解下列方程组：{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