cho 6,4g Oxi tác dụng với Ca
a) tính khối lượng chất tạo thành canxi
b) lấy toàn bộ chất tạo thành tác dụng với CO2 tạo ra CaCO3
tính thể tích CO2 cần dùng
tính khối lượng CaCO3 tạo thành
c) các loại phản ứng trên thuộc loại phản ứng gì ?
K
Khách
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21 tháng 2 2021
c) \(\frac{x^3-1}{x^2+x+1}+\frac{x^5-1}{x^4+x^3+x^2+x+1}+\frac{x^7-1}{x^6+x^5+x^4+x^3+x^2+x+1}-2006\left(x-1\right)=0\)
\(\Leftrightarrow\frac{\left(x-1\right)\left(x^2+x+1\right)}{x^2+x+1}+\frac{\left(x-1\right)\left(x^4+x^3+x^2+x+1\right)}{x^4+x^3+x^2+x+1}+\frac{\left(x-1\right)\left(x^6+x^5+x^4+x^3+x^2+x+1\right)}{x^6+x^5+x^4+x^3+x^2+x+1}\)\(-2006\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)+\left(x-1\right)+\left(x-1\right)-2006\left(x-1\right)=0\)
\(\Leftrightarrow3\left(x-1\right)-2006\left(x-1\right)=0\)
\(\Leftrightarrow-2003\left(x-1\right)=0\)
\(\Leftrightarrow x-1=0\)
\(\Leftrightarrow x=1\)
Vậy nghiệm của PT là x=1
Chú thích : Bài này sử dụng hằng đẳng thức mở rộng : \(a^n-1=\left(a-1\right)\left(a^{n-1}+a^{n-2}+...+a^2+a+1\right)\)với n là số lẻ .
21 tháng 2 2021
nếu là phân tích đa thức thành nhân tử:
(x^2+2x)+(3x+6)
=x(x+2)+3(x+2)
=(x+2)(x+3)
22 tháng 2 2021
Circle the best word/phrase (A,B,C or D) to complete the sentences below.
1, Australia is composed of seven _____ .
A. nations B. countries C. states D. capitals
2, _____ you ever been to any English speaking countries ?
A. Do B. Have C. Were D. Are
3, What can be done to protect people from _____ disasters?
A. environment B. environmental C. environmentally D. environmentalist
4, __________ should we meet on Sunday ? - Because I have to do some shopping first, then let's meet at 10 a.m
A. Why B. Where C. What time D. When
5, By the time we got to the cinema, the film ______.
A. started B. had started C. starting D. starts
6, A person who _______ the bagpipes is called a piper.
A. plays B. performs C. entertains D. brings
7, Don't drink that water. It's ______.
A. damaged B.dumped C. contaminated D. disppeared
8. The team's succes was largely ____ to her efforts.
A. because B. due C. since D. although
9. If you ______ the president, what would you do to help the environment ?
A. are B. had been C. were D. have
10, - " I've passed my driving test."
- " _____"
A. Congratulations! B. That's a good idea. C. It's nice of you to say so. D. Do you ?
24 tháng 2 2021
Circle the best word/phrase (A,B,C or D) to complete the sentences below.
1, Australia is composed of seven _____ .
A. nations B. countries C. states D. capitals
2, _____ you ever been to any English speaking countries ?
A. Do B. Have C. Were D. Are
3, What can be done to protect people from _____ disasters?
A. environment B. environmental C. environmentally D. environmentalist
4, __________ should we meet on Sunday ? - Because I have to do some shopping first, then let's meet at 10 a.m
A. Why B. Where C. What time D. When
5, By the time we got to the cinema, the film ______.
A. started B. had started C. starting D. starts
6, A person who _______ the bagpipes is called a piper.
A. plays B. performs C. entertains D. brings
7, Don't drink that water. It's ______.
A. damaged B.dumped C. contaminated D. disppeared
8. The team's succes was largely ____ to her efforts.
A. because B. due C. since D. although
9. If you ______ the president, what would you do to help the environment ?
A. are B. had been C. were D. have
10, - " I've passed my driving test."
- " _____"
A. Congratulations! B. That's a good idea. C. It's nice of you to say so. D. Do you ?