z=y+(L-x)(dy/dx),对x求导,怎么得的dz/dx=(dy/dx)-(dy/dx)+(L-x)(d^2y/d

d^2y/dx^2=(dy/dx)'×(dy/dx),另外请解释下dx,dy的含义,dx和dy是指x=...和y=... d(x+y)=dx+dy, 请教数学高手(d/dx)X^2+(d/dx)Y^2=0怎么推出2X+2Y(dy/dx)=0,是对X求导吗? dx/dy=1/y',求d^2x/dy^2 .为什么d^2x/dy^2不等于dx/dy求导?一个是二阶导数,一个是一阶导 求微分方程的通解：x^2(d^2y/dx^2)=(dy/dx)^2+2x(dy/dx) 微分方程(x+y)(dx-dy)=dx+dy的通解 f(x,y,z)=0,z=g(x,y),求dy/dx,dz/dx (x^2)dy+（y^2)dx=dx-dy dy/dx=x+y y=tg(x+y),求导dy/dx得什么? d{cos(x-y)=sin(x-y)(dx-dy)这里dx-dy是什么意思呢? 求函数：z^x=y^z的,dz/dx,dz/dy,