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\(a,PTHH:CaCO_3\xrightarrow{t^o}CaO+CO_2\\ b,BTKL:m_{CaCO_3}=m_{CaO}+m_{CO_2}\\ c,m_{CaO}=m_{CaCO_3}-m_{CO_2}=10-4,4=5,6(tấn)\)
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\(1.Al_2O_3+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2O\\ 2.N_2+3H_2-^{t^o,p,xt}\rightarrow2NH_3\\ 3.2Mg+O_2-^{t^o}\rightarrow2MgO\\ 4.4Al+3O_2-^{t^o}\rightarrow2Al_2O_3\\ 5.2H_2+O_2-^{t^o}\rightarrow2H_2O\\ 6.2Al+6HCl\rightarrow2AlCl_3+3H_2O\\7. Zn+2HCl\rightarrow ZnCl_2+H_2\\ 8.2Al+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2\)
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Bài 1:
a: \(A=8\sqrt{2}-15\sqrt{2}-8\sqrt{2}=-15\sqrt{2}\)
b: \(B=-\sqrt{7}\)
Bài 1:
\(A=8\sqrt{2}-15\sqrt{2}-8\sqrt{2}=-15\sqrt{2}\\ B=\dfrac{-\sqrt{7}\left(1-\sqrt{2}\right)}{1-\sqrt{2}}=-\sqrt{7}\\ C=\sqrt{\left(\sqrt{2}+\sqrt{5}\right)^2}-\sqrt{5}=\sqrt{2}+\sqrt{5}-\sqrt{5}=\sqrt{2}\)
Bài 2:
\(a,\Leftrightarrow x+2=9\Leftrightarrow x=7\\ b,ĐK:x\ge-5\\ PT\Leftrightarrow2\sqrt{x+5}-6\sqrt{x+5}=-16\\ \Leftrightarrow\sqrt{x+5}=\dfrac{-16}{-4}=4\\ \Leftrightarrow x+5=16\\ \Leftrightarrow x=11\left(tm\right)\)
Bài 4:
Gọi góc đó là \(\alpha\) thì \(\sin\alpha=\dfrac{6}{8}\approx\sin49^0\Leftrightarrow\alpha\approx49^0\)
Vậy góc tạo bởi thang và mặt đất xấp xỉ 49 độ
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a: Xét ΔAHB vuông tại H và ΔCHA vuông tại H có
góc HAB=góc HCA
=>ΔAHB đồng dạng với ΔCHA
b,c: góc FAE+góc FHE=180 độ
=>FAEH nội tiếp
=>góc HFE=góc HAE=góc C
Xét ΔHFE vuông tại H và ΔHCA vuông tại H có
góc HFE=góc HCA
=>ΔHFE đồng dạng với ΔHCA
=>HF/HC=HE/HA
=>HF*HA=HC*HE
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d: ta có: \(C=3+3^3+3^5+...+3^{1991}\)
\(=3\left(1+3^2+3^4\right)+...+3^{1987}\left(1+3^2+3^4\right)\)
\(=91\cdot\left(3+...+3^{1987}\right)⋮13\)
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1. loves a birthday cake which I made for her very much.
2. suddenly colapsed when i was sitting on it .
3. The woman who is my president is Mr.Hung's wife.
4. Even though she is good at English ,they didn't accept her.
5. The novel which my uncle wrote 2 years ago is very intersting.
6. Have you ever spoken to the Browns who live next door ?
7. Where is the girl who sells the tickets ?
8. Though he had a serious financial problem , he didn't ask any friend of him for help.
9. Is MR.Pike ,who is from Australia, your teacher?
10. The book which will interesst children of all ages has just been published.
[Mik nghĩ chỗ the book này là nên chia bị động chứ nó không thể tự publish (xuất bản) được ]
11. David has a Master's degree , he works as a store clerk.
12. There are some word which are vẻy difficult to translate.
13. That is the most beutiful woman (whom) I have ever met.
14. All the things which we bought this morning are for the birthday party.
15. This is the most difficult question (which) I have ever met.
16. I met many people , their cattle and vehicles that went to the fair. ( vừa có người vừa có vật thì dùng ĐTQH là that )
17. They gave me four cakes , one of which was spoiled.
18. Intel computers ,which are made in Indian, are very good.
19. The building which was destroyed in the earthquake has now been rebuilt.
20. Although Mr John is over 80 years , he walks 10km everyday.
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\(\frac{3\left(x-2\right)}{4}\div\frac{2-x}{2}=\frac{3\left(x-2\right)}{4}\times\frac{-2}{x-2}=\frac{-3}{2}\)
học tốt
Rút gọn nhé !
\(\frac{3}{4}.\left(x-2\right):\frac{1}{2}.\left(2-x\right)=\frac{3x-6}{4}.2.\left(2-x\right)\)
\(=\frac{3x-6}{4}.\left(4-2x\right)=\frac{\left(3x-6\right).\left(4-2x\right)}{4}\)
\(=\frac{\left(12x-24\right)-\left(6x^2+12x\right)}{4}=\frac{-24-6x^2}{4}\)
\(=\frac{-12-3x^2}{2}=\frac{-3.\left(4+x^2\right)}{2}\)