问题
填空题
若曲线f(x)＝ax3＋ln x存在垂直于y轴的切线，则实数a的取值范围是
________．
答案
(－∞，0)
f′(x)＝3ax2＋
，∵f(x)存在垂直于y轴的切线，∴f′(x)＝0有解，即3ax2＋＝0有解，∴3a＝－
，而x>0，∴a∈(－∞，0)．
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若曲线f(x)＝ax3＋ln x存在垂直于y轴的切线，则实数a的取值范围是
________．
(－∞，0)
f′(x)＝3ax2＋，∵f(x)存在垂直于y轴的切线，∴f′(x)＝0有解，即3ax2＋＝0有解，∴3a＝－，而x>0，∴a∈(－∞，0)．
完形填空，从每小题所给的四个选项中，选出最佳答案填空。（共10小题，每小题1分，满分10分） One day I go to my good friend Bruce’s home. There are four people in his family. His parents 1 both English teachers. He 2 a little brother. 3 name is Peter. Peter is only five years old. He doesn't 4 to school. So he doesn't know how to read or write. I see Peter sitting at the table with a pen 5 his hand. "What are you doing, Peter?" I ask. "I'm writing 6 my friend, Bill." says Peter. "But how 7 write?" asks Bruce. "You don't know the words, because(因为) you don’t go to 8 ". With a smile, Peter says. "But it doesn't matter（没关系）because my 9 and I know the words on the moon. I write to him in the moon language. It’s easy(容易的) for him to read my letter. I tell him an interesting story. I’m sure Bill will be 10 to read it.” What an interesting answer it is!
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