题目

阅读材料：基本不等式 ，当且仅当 时，等号成立.其中我们把 叫做正数a、b的算术平均数， 叫做正数a、b的几何平均数，它是解决最大 小 值问题的有力工具. 例如：在 的条件下，当x为何值时， 有最小值，最小值是多少？ 解 ，，即是， 当且仅当 时，即 时， 有最小值，最小值为2. 请根据阅读材料解答下列问题： （1） 若 ，函数 ，当x为何值时，函数有最值，并求出其最值， （2） 当 时，式子 成立吗？请说明理由.14．Online shopping is coming into fashion in most cities，where people are able to make full use of the rapidly-developed Internet technology．Nowadays，can we find a person（61）who/thathasn't experienced online shopping？Definitely not．    Online shopping（62）is welcomed（welcome） by most people due to various reasons．From the perspective of the consumer，it can save some time for people who don't have much spare time．Just click the mouse，they can get（63）what/whateverthey want while staying at home．For the retailers（ 零售商），it can cut some costs for those who don't have much circulating funds．（64）Compared（compare） with the traditional trade mode，it saves them the need to rent a house．（65）However，there are still some（66）disadvantages（advantage） in online shopping．First，a face-to-face deal makes online shopping less（67）reliable（rely） and trustworthy．Second，people will lose the fun of bargain．     （6）Itis undeniable that shopping on the Internet has become an irresistible trend in modern society．It's of great urgency that we need to make the relative laws with the rapid（69）development（develop） of online shopping．Only in this way can we enjoy the pleasure and convenience of online shopping without the concern of（70）being cheated（cheat）．