Tính \(B= 1:{ {1\over 2} + {1\over3} +...+ {1\over2012} \over { 2011\over1} + {2010\over2}+...+{1\over2011}}\)
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Vũ Cao Minh⁀ᶦᵈᵒᶫ ( ✎﹏IDΣΛ亗 )
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26 tháng 8 2019
\(A=1+3+3^2+3^3+...+3^{99}\)
\(\Rightarrow3A=3+3^2+3^3+...+3^{100}\)
\(\Rightarrow3A-A=2A=\left(3+3^2+3^3+...+3^{100}\right)-\left(\text{}\text{}\text{}1+3^2+3^3+...+3^{99}\right)\)
\(\Rightarrow2A=3^{100}-1\Rightarrow A=\frac{3^{100}-1}{2}\)
B
29 tháng 6 2023
1. My father still hasn’t really recovered from the death of my mother.
A. went over B. got over C. took over D. looked over
2. I can’t _____ walking. Can we stop and have a short rest?
A. go on B. get on C. go up D. get up
3. When you are finished using the computer, can you please _____ it off.
A. take B. turn C. do D. go
4. When the alarm went off, everyone proceeded calmly to the emergency exits.
A. fell B. exploded C. called D. rang
5. Mrs. Jones's husband passed away fast Friday. We’re all shocked by the news.
A. got married B. divorced C. died D. were on business
6. If you want to be healthy. you should ________ your bad habits in your lifestyles.
A. give up B. call off C. break down D. get over
7. Try to study harder to catch ________ your classmates.
A. up B. up with C. out D. with
8. Don’t be impatient ! I ‘m sure he will turn ________ on time
A. up B. round C. on D. off
9. Go _______ this book because it has the information you need.
A. over B. by C. off D. on
10. My husband spends far more time helping our three kids ___ homework and studying for tests than I do.
A. on B. to C. with D. in
29 tháng 6 2023
1. My father still hasn’t really recovered from the death of my mother.
A. went over B. got over C. took over D. looked over
2. I can’t _____ walking. Can we stop and have a short rest?
A. go on B. get on C. go up D. get up
3. When you are finished using the computer, can you please _____ it off.
A. take B. turn C. do D. go
4. When the alarm went off, everyone proceeded calmly to the emergency exits.
A. fell B. exploded C. called D. rang
5. Mrs. Jones's husband passed away fast Friday. We’re all shocked by the news.
A. got married B. divorced C. died D. were on business
6. If you want to be healthy. you should ________ your bad habits in your lifestyles.
A. give up B. call off C. break down D. get over
7. Try to study harder to catch ________ your classmates.
A. up B. up with C. out D. with
8. Don’t be impatient ! I ‘m sure he will turn ________ on time
A. up B. round C. on D. off
9. Go _______ this book because it has the information you need.
A. over B. by C. off D. on
10. My husband spends far more time helping our three kids ___ homework and studying for tests than I do.
A. on B. to C. with D. in
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