题目5.设点(1,3)是曲线 =a(x)^3+b(x)^2+1 的拐点,则a、b的值是 ()-|||-A. =1, b=-3-|||-B. a=-1 =3-|||-C. =dfrac (1)(3), b=-1-|||-D. =-dfrac (1)(3) =1题目解答答案