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13 . b ) SH \(\perp\left(ABCD\right)\Rightarrow SH\perp DI\) .
Dễ dàng c/m : DI \(\perp HC\) . Suy ra : \(DI\perp\left(SHC\right)\Rightarrow DI\perp SC\) ( đpcm )
Thấy : \(\left(SBC\right)\cap\left(ABCD\right)=BC\)
C/m : SB \(\perp BC\) . Thật vậy : \(BC\perp AB;BC\perp SH\Rightarrow BC\perp\left(SAB\right)\Rightarrow BC\perp SB\)
Có : \(AB\perp BC\) nên : \(\left(\left(SBC\right);\left(ABCD\right)\right)=\left(SB;AB\right)=\widehat{SBA}=60^o\)
- Khi dùng một chiếc kim nhọn châm vào thân thủy tức, xung thần kinh sẽ lan nhanh ra khắp mạng lưới thần kinh, làm cho thủy tức co toàn bộ cơ thể.
- Phản ứng của thủy tức là phản xạ vì thủy tức có tổ chức hộ thần kinh.
A
9 km 26 m = 9,026 km
892mm = 0,892 mm
4m 783 mm = 47,83 dm
106 m = 1,06hm
8 dm 9 mm = 0,809m
1. A. celebrate B. together C. restaurant D. organize
2. A. pollution B. awareness C. disappear D. addition
3. A. apple B. butter C. mother D. advance
4. A. protection B. referee C. dictation D. increasing
5. A. carriage B. damage C. survive D. lightning
6. A. generosity B. occurrence C. priority D. memorial
1. A. celebrate B. together C. restaurant D. organize
2. A. pollution B. awareness C. disappear D. addition
3. A. apple B. butter C. mother D. advance
4. A. protection B. referee C. dictation D. increasing
5. A. carriage B. damage C. survive D. lightning
6. A. generosity B. occurrence C. priority D. memorial
\(P=\dfrac{x+2\sqrt{x}+x-2\sqrt{x}}{x-4}.\dfrac{x-4}{-2\sqrt{x}}=\dfrac{2x}{-2\sqrt{x}}=-\sqrt{x}\)
\(P=-\sqrt{x}=-\sqrt{4}=-2\left(đpcm\right)\)
refer
1. “Open the door,” he said to them.
-He told them to open the door.
2. “Where are you going?” he asked her.
-He asked her where she was going
3. “Which way did they go?” he asked.
-He asked which way they had gone
4. “Bring it back if it doesn’t fit”, I said to her.
-I told her to Bring it back if it didnt fit
5. “Don’t try to open it now,” she said to us.
-She told us to not try to open it then
6. “Is it going to be a fine day today?” I asked her.
-I asked her if it was going to be a fine day that day
7. “He’s not at home”, she said.
-She said that he was not at home
8. “Is the bus station far away?” the girl asked.
-The girl wanted to know if the bus station was far away
9. “Don’t stay late Ann” Tom said.
-Tom told Ann not to stay late
10. “Please let me borrow your car,” he said to her.
-He asked het to let him borow her car
11. “Jean, have you seen my gloves?” Thomas asked.
-Thomas asked Jean if he had seen his gloves
12. Don’t leave the window open, Mary”, I said.
-I told Mary not to leave the window open
13. “I’ll have a cup of tea with you,” she said.
She said that she would have a cup of tea with me
14. “I’ll pay him if I can” she said.
-She said that she would pay him if she could
15. “What are you going to do next summer?” she asked.
- She asked us what we were you going to do the next summer
Answer:
1. B
2. D
3. D
4. A
5. B
6. C
7. D
8. D
9. B