如图,高数书上的题目.复合函数求导.答案写的不详细看不懂.

第9题：dz/dx=y+F(u)+xF'(u)(-y/x^2)=y+F(u)-yF'(u)/x
dz/dy=x+xF'(u)(1/x)=x+F'(u)
xdz/dx+ydz/dy=xy+xF(u)-yF'(u) + xy + yF'(u)=xy+xF(u) + xy = z+xy
第10题：dz/dx=y(-1/f^2)*f'*2x=-2xyf'/f^2
dz/dy=[f-f'*y*(-2y)]/f^2=(f+2f'y^2)/f^2
dz/(xdx)+dz/(ydy)=-2yf'/f^2+1/f*y + 2yf'/f^2=1/f*y=z/y^2