Problem

甲、填充題：共 8 題，每題 8 分，共 64 分。請將答案依題號順序寫在答案卷上。

6. Find an equation of the tangent line to the graph of the function $x^2y^3-y^2+xy-1=0$ at $(1,1)$. Answer : \underline{\quad(1)\quad}