y=20x^2+2x+1200 (x>12).求y最小值 用基本不等式解

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 函数,y=3x/(x^2+x+1) ,x 函数y=3x/(x^2+x+1) （x 函数y=2x/x²-x+1（x 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 (1)1200+4y=500x (2)2400+20x=20y 求x, y=(2x)/x-1化简成用y表示x (x-y)(y-x)-[x的平方-2x(x+y)]其中x=2分之1,y=-2 (x-y)(y-x)-[x²-2x(x+y)],其中x=1/2,y=-2 x+y=1,xy=-1/2,求x(x+y)(x-y)-x(x+y)2 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 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}] 1.(x-y)(x+y)+(x-y)+(x+y)2.x(x+2)-(x+1)(x-1),其中x=-二分之一请写清步骤,结果. x+2y=2x+y+1=7x-y 求：2x-y? 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