X^2+Y^2=36求（X+y）^2+y^2的最大值,不能求导

求y''+2y'+y=e^-x/x的通解y''+2y'+y=（e^-x）/x x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 对于(y一撇）y`=y/x(y-1)求导,我求的结果是y``=-y^2-y`x+y/x^2(y-1)^2 怎么不对啊,我的求导过程是：y`x(y-1) - [x(y-1)]` y y`xy-y`x-(y-1+xy`)y -y^2-y`x+yy``=-------------------------=----------------------=-----------------x^2 (y-1 y=2x*arctan(y/x),求y‘’ 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 2x／x-y=（）／（x-y）（x+y）求括号中的数 x+2y=2x+y+1=7x-y 求：2x-y? f(x+y,x-y)=(x^2-y^2)/2xy,求f(x,y)! 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y x^2+y^2=15,x+y=7,x＞y,求x-y f(x+y,y/x)=x^2-y^2求f(x,y) 已知x≠y,x^2-x=y^2-y,求x+y的值. f(x+y,y/x)=x^2-y^2,求f(x,y),详见里面 若|x+y-1|+（x-y-2)²=0,求代数式（x+2y)(x-2y）-（2x-y)(-y-2x)的值. 如果|X|=4 |Y|=2 且|X+Y|=X+Y 求X+Y 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y