搜题请搜索小程序“爱下问搜题”
问题 填空题

设二次函数f（x）=x2+ax+5对于任意t都有f（t）=f（-4-t），且在闭区间[m，0]上有最大值5，最小值1，则m的取值范围是______．

答案

因为已知条件：对于任意t都有f（t）=f（-4-t），

所以二次函数的对称轴为x=-2

所以-

a
2
=-2

所以a=4

所以f（x）=x2+4x+5

因为f（-2）=1，f（0）=5

因为在闭区间[m，0]上有最大值5，最小值1，

所以-4≤m≤-2

故答案为-4≤m≤-2

单项选择题

Questions from 31 to 35 are based on the following passage: Against this background, the WTO faces several daunting challenges. The first is to continue bringing down tariffs on traded goods. Average penalties have fallen steadily since the GATT’s formation but even the most open economies retain lofty barriers: for instance, America still charges a tariff of 14.6% on import of clothing, five times higher than its average levy.Resistance to tariff cuts is pest in agriculture. According to Tim Josling, a trade expert at Stanford University, tariffs and other barriers on farm goods average a crippling 40% worldwide and create distortions that “destroy huge amounts of value”. A new set of global farm talks is planned to start in 1999. At the least, you might think, these could lock in impressive reforms in Latin America and encourage further watering-down of the European Union’s Common Agricultural Policy. But they will prove difficult: squabbles over agriculture almost sank the Uruguay round.

When is a new set of global farm talks planned to start（）

A．1980

B．1990

C．2001

D．at the end of 20 th century
查看答案
单项选择题

一般鼻咽癌首发症状是（）

A.耳部症状

B.脑神经症状

C.涕中带血

D.颈深部上群淋巴结肿大

E.远处转移
查看答案