题目5.设函数 y=f(x) 由方程 ^2+(x)^2-2x=1 确定,则 dfrac (dy)(dx)=[ ] ()-|||-A. dfrac (x-1)(y) B. dfrac (1-x)(y) C. dfrac (y)(1-x) D. dfrac (y)(x-1)题目解答答案