题目

已知一个正数的两个不同的平方根为和．求和的值． 答案：【答案】a=-2；x=49．【解析】正数x有两个平方根，分别是2a−3与5−a，所以2a＋2与5−a互为相反数，可求出a；根据x＝（2a−3）2，代入可求出x的值．解：由题意，得：（2a﹣3）+（5﹣a）＝0，解得a＝﹣2，∴x＝（2a﹣3）2＝（﹣7）2＝49．These are all good team sports and will help you ______ your strength and you will meet lots of people atthe same time. [     ]A. grow up B. give upC. mix up D. build up