令t1=xz,t2=z-y,则z=f(t1,t2),用fi'表示f(t1,t2)中对t1(第i个中间变量)的偏导数,则有
dz=f1'*d(xz)+f2'*d(z-y)
=f1'*(zdx+xdz)+f2'(dz-dy)
移项化简,得
dz=(zf1'dx-f2'dy)/(1-xf1'-f2')
令t1=xz,t2=z-y,则z=f(t1,t2),用fi'表示f(t1,t2)中对t1(第i个中间变量)的偏导数,则有
dz=f1'*d(xz)+f2'*d(z-y)
=f1'*(zdx+xdz)+f2'(dz-dy)
移项化简,得
dz=(zf1'dx-f2'dy)/(1-xf1'-f2')