Problem

甲、填充題：共 8 題，每題 8 分，共 64 分。請在答案卷上列出題號依序作答。

6. Let $z=f(x,y)=\ln(xy)^{1/2}$. Find the approximate change in $z$ when the point changes from $(5,10)$ to $(5.03,9.96)$. Answer : \underline{\quad(1)\quad}