求y=(x/4)^2+[(100-x)/4]^2的导数正确过程是y=(x/4)^2+[(100-x)/4]^2=（2x^2-200x+10000)/16 y'=(4x-200)/16=0 x=50我想问的是为什么不能这么算y'=[(x/4)^2]'+{[(100-x)/4]^2}'=x/2+(100-x)/2=0 这样算x就无解了,这种算法哪里错

2x+4y=100 x+y=49求x和y值, 如果|X|=4 |Y|=2 且|X+Y|=X+Y 求X+Y 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? x*x+y*y-2x+4y+5=0求x, 不解方程组2x-y=10 x+3y=1/100 求（2x-y)²-（2x-y)²（x-4y)的值 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y 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 y=2x+4/x 求极值~y=2x+4/x 求极值 已知x=3分之一,y=-2分之一,求代数式x-(x+y)+(x+2Y)-(x+3y)+(x+4y)...-(x+2009y) y*y*y*y+2x*x*x*x=4x*x*y 求x等于几,y等于几,写出所有选项! 求值域y=x/x^2+2x+4 求y=(5x-1)/(4x+2) (x 求函数y=(3x+4)/(x-2) (x 2x+3y=100 求x+y=? 求值域 1,y=(x+2)/(x*x+3x+6) 2,y=3x/(x*x+4) 已知:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y