已知函数y=
|
y(x2+1)=mx2+4
x+n，(y-m)x2-43
x+y-n=03
显然y=m可以成立，当y≠m时，方程(y-m)x2-4
x+y-n=03
必然有实数根，
∴△=48-4（y-m）（y-n）≥0，
即y2-（m+n）y+mn-12≤0，而-1≤y≤7
∴-1和7是方程y2-（m+n）y+mn-12=0的两个实数根
则
，m=1，n=5m+n=6 mn-12=-7
∴y=x2+4
x+53 x2+1
书面表达 15分 假如你叫张宾，Jimmy是你的笔友，他下个月就要到中国旅游。请你根据下面e-mail给他介绍国内非常值得一去的地方。
词数：80左右。开头和结尾已经写好，不计入总词数。 参考词汇：imperial adj. 皇帝的steep adj.陡峭的 the Terra Cotta Warriors秦陵兵马俑 Dear Jimmy, I am very glad to hear that you’ll come to China for a visit next month. Now I will teel you something about the places of interest in China. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Oh, I must stop now. I hope you will have a good trip! Good luck! Yours Zhang Bin |