分类：教育/科学-学习帮助
问题：复合函数的偏导数z=xyln(x+y).求(便z/偏x）/（便z? 
附件在这里，。请帮下，谢谢了
回答：pz/px = yln(x+y) + xy/(x+y)
pz/py = xln(x+y) + xy/(x+y);

(pz/px)*(pz/py)
=(yln(x+y) + xy/(x+y))*(xln(x+y) + xy/(x+y))
=xy(ln(x+y))^2 + xyln(x+y) +(xy)^2/(x+y)^2