题目

Many of us enjoy watching animals in the world. But do you know they can teach us. Geese(雁), for example, teach a very good lesson about 1 .In the fall, Canada geese fly to the warm south to 2 Canada’s cold winter. They lift off in no order. Yet 3 they form a V shape, with one bird leading the group. This V shape allows geese to  4  energy. When the front bird moves its wings up and down, the resulting force of the air lifts the next one. This continues down the line. The bird 5 has the hardest job. When it gets 6 ,it moves behind, and another bird moves into the lead. By sharing设是定义在上的偶函数，对，都有，且当时， ．若在区间内关于的方程恰有3个不同实根，则的取值范围是（ ）A． B． C． D．【答案】A【解析】试题分析：由，得，所以函数是周期为4的函数．又是偶函数，且时，＝，所以时，．方程在内有三个根，即函数与函数在内有三个交点，作出函数与图像如图所示，则两个图像在内恰有三个交点的条件是，解得，故选B．考点：1、指数函数与对数函数的图象与性质；2、函数的零点与方程根的关系；3、不等式的解法．【方法点睛】方程的根为对应函数的零点，而函数的零点通常还可转化为两个函数的交点，因此求解函数的零点个数通常有两种方法：（1）直接法，即求解出所有的零点；（2）数形结合法，即转化为原函数的图象与轴的交点个数或分解为两个函数相等，进而判断两个函数图象的交点个数，此法往往更实用．而函数函数的图象要求正确，特别是关键点的作法．【题型】选择题【适用】较难【标题】【百强校】2016届江西省临川一中高三上学期期中文科数学试卷（带解析）【关键字标签】【结束】 设，，若，则= ．