题目

Cell phones are so cheap that almost all people can afford it. 48._____ you go, you can see people holding cell phones doing different things. Our life style has changed greatly 49. _____ of the widespread of mobile phones. Mobile phones change 50._____ way we contact others. In the past, we contacted our families, relatives and friends by writing letters 51._____ just going to a certain area to make a phone call. Now, if we want to contact them, all we need to do is to take out our cell phone, dial the number and then we can reach 52._____ in a minute. With a cell phone, we 53._____ 已知A（a，b）和（c，d）关于y轴对称，试求3a+3c+2bd．