题目

已知x1，x2是方程x2+2x﹣7＝0的两个根，则x12+3x1+x2＝_____． 答案：【答案】5【解析】根据方程的解的定义得出x12+2x1=7，由韦达定理可得x1+x2=-2，代入原式=x12+2x1+x1+x2可得答案．∵x1，x2是方程x2+2x-7=0的两个根，∴x1+x2=-2，x12+2x1-7=0，即x12+2x1=7，则原式=x12+2x1+x1+x2=7-2=5，故答案为：5．世界的环境污染问题在变得越来越严重。根据题目《师父被熏晕过去了》漫画和下面要求写一篇关于河水污染的感想并提出保护环境的建议，内容大概包括：1. 情况。2. 原因。3. 后果。4. 措施。注意：1.信的开头已经给出，不计算在总词数内。2. 字数要求: 120左右。 One day Sun Wukong together with his master and brothers was walking across a river.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           ______________________________________________________________________________________________________________________________________________________