问题
填空题
设f（x）=log3（x+6）的反函数为f-1（x），若〔f-1（m）+6〕〔f-1（n）+6〕=27，则f（m+n）=______．
答案
∵f-1（x）=3x-6
故〔f-1（m）+6〕•〔f-1（x）+6〕=3m•3n =3m+n =27，
∴m+n=3，
∴f（m+n）=log3（3+6）=2．
故答案为 2．
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设f（x）=log3（x+6）的反函数为f-1（x），若〔f-1（m）+6〕〔f-1（n）+6〕=27，则f（m+n）=______．
∵f-1（x）=3x-6
故〔f-1（m）+6〕•〔f-1（x）+6〕=3m•3n =3m+n =27，
∴m+n=3，
∴f（m+n）=log3（3+6）=2．
故答案为 2．
| 完形填空。 |
| Lucy and Lily are with their mother. They are sitting in the park. The children are tired. Their mother is tried, too. Lucy: Can we sit l the grass, Mum? Mum: No, you can't, Lucy. The grass is wet. Lucy: OK, Mum. I can see a bench near that tree. We can sit 2 . Mum: No, you can't, children. The bench is wet, too. Lily: It's not raining. The bench isn't wet. Mum: Can you see a notice on the bench, Lily? Lily: Yes, I can. Mum: What 3 the notice say? Lily: I 4 read it. Can you read the notice, Lucy? Lucy: Yes, I can. It 5 "Wet Paint". |
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