题目

Shanghai is one of ______________ in the world . A more big city   B the biggest city   C the biggest cities 答案：C 设函数f(x)＝lnx－ax2－bx (1)若x＝1是f(x)的极大值点，求a的取值范围． (2)当a＝0，b＝－1时，函数F(x)＝f(x)－λx2有唯一零点，求正数λ的值．