Đáp án:
b )
√$\frac{x-2√x +1}{x+2√x +1}$
=√$\frac{(√x-1)^2}{(√x+1)^2}$
=l$\frac{√x-1}{√x+1}$ l
Giải thích các bước giải:
Điều kiện:`x>=0`
`b)B=\sqrt{(x-2\sqrt{x}+1)/(x+2\sqrt{x}+1)}`
`B=\sqrt{(\sqrt{x}-1)^2/(\sqrt{x}+1)^2}`
`B=|(\sqrt{x}-1)/(\sqrt{x}+1)|`
Vì `\sqrt{x}+1>=1>0`
`=>B=|\sqrt{x}-1|/(\sqrt{x}+1)`.
Giúp với bài 5 nha hứa sẽ cho full 60đ
1. “Where do you think Rooney is today?". "I have no idea. He..............late." A. should have left B. would sleep C. would have sleep D. may have slept 2. Barbate painted his bedroom black. It looks dark and dreary. He..............a different color. A. had to choose B. must have chosen C. should have chosen D. could have been choosing 3. The children.............."thank you" to you when you gave them their gifts. A. will have said B. should have said C. must say D. should say 4. If we had known your new address, we..............to see you. A. came B. will come C. would have come D. would come 5. These two boys look identical. They..............twins. A. must have been B. should be C. must be D. should have been 6. You've been working non-stop for ten hours. You..............be really tired. A. should B. must C. would rather D. ought to 7. The fortune teller predicted that..............inherit a big fortune before the end of this year. A. will B. she will C. would D. she would 8. I'm feeling very tired this morning. I..............have stayed up late last night. A. couldn't B. shouldn't C. mustn't D. to stopping 9. He helped her, but it was not necessary. He needn't..............her. A. help B. to help C. be helping D. have helped 10. "..............you like to play a game of tennis?" "I'd love to." A. Could B. Will C. Do D. Would 11. His letter is full of mistakes. He..............the mistakes carefully before sending it. A. must have checked B. should have checked C. could have checked D. can have checked 12. "I bought two bottles of milk." "You..............have bought milk; we have heaps of it in the house." A. couldn't B. needn't C. mustn't D. hadn't 13. When I first went to England, I..............English, but I..............it. A. can read; can't speak B. can read; couldn't speak C. could read; couldn't speak D. could read; can't speak 14. The car plunged into the river. The driver..............out but the passengers were drowned. A. is able to get B. could get C. was able to get D. can get 15. I..............got lost and..............ask a policeman the way. A. have to B. must have to C. had to D. would 16. We have some days off after the exam..............spend some time together? A. Let B. Shall I C. Shall we D. Would you like 17. You..............ring the bell; I have a key. A. may not B. needn't C. mustn't D. couldn't 18. You..............drink this; it's poison. A. must B. needn't C. mustn't D. shouldn't 19. Nobody knows how people first came to these islands. They..............have sailed from South America. A. might B. must C. should D. had 20. She felt ill and..............leave early. A. has to B. must C. had to D. ought
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