高数，这题怎么做的，我怎么算都不对
1个回答
展开全部
z=xln(x+y)
∂z/∂x=x/(x+y) + ln(x+y)
∂z/∂y=x/(x+y)
∂²z/∂x²=(x+y-x)/(x+y)² +1/(x+y)
=(y+x+y)/(x+y)²
=(x+2y)/(x+y)²
∂²z/∂y²=-x/(x+y)²
∂²z/∂x∂y=-x/(x+y)² +1/(x+y)
=(-x+x+y)/(x+y)²
=y/(x+y)²
∂z/∂x=x/(x+y) + ln(x+y)
∂z/∂y=x/(x+y)
∂²z/∂x²=(x+y-x)/(x+y)² +1/(x+y)
=(y+x+y)/(x+y)²
=(x+2y)/(x+y)²
∂²z/∂y²=-x/(x+y)²
∂²z/∂x∂y=-x/(x+y)² +1/(x+y)
=(-x+x+y)/(x+y)²
=y/(x+y)²
本回答由提问者推荐
已赞过
已踩过<
评论
收起
你对这个回答的评价是？
推荐律师服务：
若未解决您的问题，请您详细描述您的问题，通过百度律临进行免费专业咨询
