题目

设m、n是一元二次方程x2＋3x－7＝0的两个根，则m2＋4m＋n＝      ． 答案：【考点】根与系数的关系；一元二次方程的解． 【分析】由α，β是一元二次方程x2+3x-7=0的两个根，得出α+β=-3，α2+3α=7，再把a2+4a+β变形为a2+3α+α+β，即可求出答案． 【解答】解：∵α，β是一元二次方程x2+3x-7=0的两个根， ∴α+β=-3，α2+3α=7， ∴a2+4a+β=a2+3α+α+β=7-3=4， 故答案为：4． 【点评】本题考查 完形填空。      Ben and his wife Susan were on their way to have dinner with their friends, Ian and Betty. It was a dark,   1   night, and they did not know the road very well. They   2   through Cookstown, until they found   3   they thought was the road to Dorling,   4   Ian and Betty lived.   5   it soon became clear that they were not on the road to   6   at all. The road that they were on was getting   7  , and there were not other   8   on it. The wind was blowing   9   with every minute that passed.         They came to a small   10  . They drove past a church, and then two houses without lights on. There was   11   about to tell them where they   12  , or where the road went. Just then Ben saw a telephone-box, fifty metres or so further on. While he walked   13   along the road to see if there was a name outside the church, Susan   14   Ian and Betty to tell that they were still   15  .         Betty was just saying that the   16  as already rather dry, when Ben came back to the   17  , his head down   18   the wind. He said that there was a tree   19   across the road, and that the telephone lines were down, Susan heard   20   more from Betty about the dinner. (     )1. A. cloudy(     )2. A. rode(     )3. A. what  (     )4. A. there     (     )5. A. And     (     )6. A. Coodstown (     )7. A. narrower (     )8. A. bikes (     )9. A. hard (     )10. A. house  (     )11. A. somebody  (     )12. A. were  (     )13. A. forward  (     )14. A. wrote  (     )15. A. at home (     )16. A. dinner (     )17. A. telephone box (     )18. A. on (     )19. A. standing  (     )20. A. something  B. rainy       B. ran       B. that       B. which        B. But        B. their own home B. wider      B. cars      B. heavily      B. village     B. nobody      B. went      B. ahead      B. explained   B. on their way B. weather      B. church       B. to        B. lying      B. a little      C. windy      C. walked       C. which       C. where       C. So         C. Dorling       C. longer     C. trains     C. harder     C. church        C. anybody       C. passed        C. around       C. visited       C. in Cookstown    C. coat        C. houses       C. against      C. laying     C. much          D. snowy               D. drove              D. when                D. that                D. Or                  D. a village           D. farther             D. carts               D. more heavily        D. telephone box       D. everybody           D. drove               D. back                D. telephoned          D. in the church       D. water               D. village             D. into                D. growing             D. nothing