Tính \(B= 1:{ {1\over 2} + {1\over3} +...+ {1\over2012} \over { 2011\over1} + {2010\over2}+...+{1\over2011}}\)
Bài 1:Tính
a) A= (-3)+(-6)+(-9)+...+(-90)
b) \(B = {3\over 5.7}+{3\over 7.9}+{3\over 9.11}+...+{3\over97.99}\)
Bài 2:
a)So sánh: \( A = {15^30-1 \over 15^29-1} và B= {15^31-1\over 15^30-1}\)
b)Tìm chữ số a, b biết: 4a5b \(⋮\)4, 4a5b : 3 dư2
Bài 3:Tính A/B:
\(A = {1\over2}+{1\over3}+{1\over4}+...+{1\over308}+{1\over309} \)
\(B = { 308\over1}+{ 307\over 2}+{ 306\over 3}+...+{ 3\over306}+{ 2\over 307}+{ 3\over 308}\)
\( {x+1{} \over 2012}+{x+2{} \over 2011}-{x+3{} \over 2010}-{x+4{} \over 2009}. Tính\)
chứng minh rằng: \({1\over2}+{1\over3}+{1\over4}+...+{1\over63}>2\)
A=1+3+3^2+3^3+...+3^100
B=\({1 \over 2}\)+(\({1 \over2}\))^2+(\( {1 \over 2}\))^3+...+(\({1 \over 2}\))^99
C=5^100-5^99+5^98-5^97+...+5^2-5+1
\(A=1+3+3^2+3^3+...+3^{99}\)
\(\Rightarrow3A=3+3^2+3^3+...+3^{100}\)
\(\Rightarrow3A-A=2A=\left(3+3^2+3^3+...+3^{100}\right)-\left(\text{}\text{}\text{}1+3^2+3^3+...+3^{99}\right)\)
\(\Rightarrow2A=3^{100}-1\Rightarrow A=\frac{3^{100}-1}{2}\)
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
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
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
\(A = {3x + 2√x -3 \over x+√x -2} - {√x+1\over√x+2 }+{√x-2 \over1-√x}\)
Rút gọn giúp mình với, mình đang cần gấp lắm
\(({-1 \over2})^{513} và ({-1 \over3})^{315}\)
So sánh
Nhưng so sánh cái j cơ??? ._.
So sánh
\(({-1 \over2})^{513}và({-1 \over3})^{315}\)
So sánh gì vậy bạn
so sánh 1234565 vs 897678000
cho a,b >0. c.m:
\( {a^3 + b^3 \over a^2 + ab + b^2 } \geq {1\over3}.(a+b)\)