a) \(A=\dfrac{3}{4}.\dfrac{8}{9}.\dfrac{15}{16}.\dfrac{24}{25}.....\dfrac{120}{121}.\dfrac{143}{144}\)

= \(\dfrac{1.3.2.4.3.5.4.6....10.12.11.13}{2^2.3^2.4^2.5^2...11^2.12^2}\)

= \(\dfrac{1.2.12.13}{2^2.12^2}=\dfrac{13}{2.12}=\dfrac{13}{24}\)

b) \(B=\dfrac{5}{9}.\dfrac{21}{25}.\dfrac{45}{49}.\dfrac{77}{81}....\dfrac{357}{361}.\dfrac{437}{441}\)

= \(\dfrac{1.5.3.7.5.9.7.11.....17.21.19.23}{3^2.5^2.7^2....19^2.21^2}=\dfrac{1.3.21.23}{3^2.21^2}\)

= \(\dfrac{23}{3.21}=\dfrac{23}{63}\)

=2x2/1x3 x 3x3/2x4x4/3x5 x ... x 11x11/10x12

=2x2x3x3x4x4x...x11x11/1x3x2x4x3x5x...x10x12

= 2x3x4x...x11)x(2x3x4x...x11)/(1x2x3x4x...x11)/(1x2x3x...x10)x(2x3x4x...x11)

=11x2/1x12

=22/12

=11/6

4/3x9/8x16/15x...x121/120=\(\dfrac{2^2}{1\cdot3}\)x\(\dfrac{3^2}{2\cdot4}\)x\(\dfrac{4^2}{3\cdot5}\)x...x\(\dfrac{11^2}{10\cdot12}\)=\(\dfrac{2}{3}\)x\(\dfrac{11}{10}\)=\(\dfrac{11}{15}\)

4/3x9/8x16/15x...x121/120=\(\dfrac{2^2}{1\cdot3}\)x\(\dfrac{3^2}{2\cdot4}\)x...x\(\dfrac{11^2}{10\cdot12}\)=\(\dfrac{2}{3}\)x\(\dfrac{11}{10}\)=\(\dfrac{11}{15}\)

\(A=1+\frac{1}{3}+1+\frac{1}{8}+1+\frac{1}{15}+...+1+\frac{1}{120}=\left(1+1+...+1\right)+\left(\frac{1}{1\times3}+\frac{1}{2\times4}+\frac{1}{3\times5}+...+\frac{1}{10\times12}\right)\)\(A=10+\frac{1}{2}\times\left(\frac{2}{1\times3}+\frac{2}{2\times4}+\frac{2}{3\times5}+...+\frac{2}{10\times12}\right)=10+\frac{1}{2}\times\left(1-\frac{1}{3}+\frac{1}{2}-\frac{1}{4}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{10}-\frac{1}{12}\right)\)\(A=10+\frac{1}{2}\times\left(1+\frac{1}{2}+\left(-\frac{1}{3}+\frac{1}{3}\right)+\left(-\frac{1}{4}+\frac{1}{4}\right)+\left(-\frac{1}{5}+\frac{1}{5}\right)+...+\left(-\frac{1}{10}+\frac{1}{10}\right)-\frac{1}{11}-\frac{1}{12}\right)\)\(A=10+\frac{1}{2}\times\left(1+\frac{1}{2}-\frac{1}{11}-\frac{1}{12}\right)=10+\frac{175}{264}=\frac{2815}{264}\)

quy dong tich cheo len

Không quy đồng tích chéo được vì khi quy đồng tích chéo mẫu số rất lớn,không rút gọn được

\(\frac{3}{4}.\frac{8}{9}.\frac{15}{16}.....\frac{120}{121}\)

\(=\frac{2.3.4......10}{2.3.4.....11}.\frac{3.4.5.....12}{2.3.4.....11}\)

\(=\frac{1}{11}.6=\frac{6}{11}\)

tui ko rảnh mà gõ cái trên nhưng có chơi free fire

bạn rank j rồi

tui chs, rank vàng( mùa trc k cương)

Bài 1

1/ (-37) +14 +26 + 37

= [(-37) + 37] + 14 + 26

= 40

2/ (-24) + 6 + 10 + 24

= [(-24) + 24] + 6 + 10

= 16

3/ 15 + 23 + (-25) + (-23)

= 15 + (-25) + [23 + (-23)]

= -10

4/ 60 + 33 + (-50) + (-33)

= [33 + (-33)] + 60 + (-50)

= 10

5/ (-16) + (-209) + (-14) + 209

= [(-209) + 209] + (-16) + (-14)

= -30

6/ (-12) + (-13) + 36 + (-11)

= (-25) + 25 = 0

7/ (-16) + 24 + 16 - 34

= [(-16) + 16] + (24 - 34)

= -10

8/ 25 + 37 - 48 - 25 - 37

= (25 - 25) + (37 - 37) - 48

= -48

9/ 2575 + 37 - 2576 - 29

= (2575 - 2576) + (37 - 29)

= -1 + 8 = 7

10/ 34 + 35 + 36 + 37 -14 -15- 16 - 17

= (37 - 17) + (36 - 16) + (35 - 15) + (34 - 14)

= 10 + 10 + 10 + 10 = 40

Bài 2

1/ -7264 + (1543 + 7264)

= -7264 + 1543 + 7264

= 1543

2/ (144 - 97) - 144

= 144 - 97 - 144

= - 97

3/ (-145) - (18 - 145)

= (-145) - 18 + 145

= - 18

4/ 111 + (-11 + 27)

= 111 - 11 + 27

= 127

5/ ( 27 + 514) - (486 - 73) 

= 27 + 514 - 486 + 73

= (27 + 73) + ( 514 - 486)

= 100 + 28 = 128

6/ (36 + 79) + (145 - 79 - 36)

= 36 + 79 + 145 - 79 - 36

= (36 - 36) + ( 79 - 79) + 145 = 145

7/ 10 - [12 - (- 9 - 1)]

= 10 - [12 - (- 10)]

= 10 - [12 + 10] = 10 - 12 - 10 = - 12

8/ (38 - 29 + 43) - (43 + 38)

= 38 - 29 + 43 - 43 - 38

= (38 - 38) + (43 - 43) - 29 = - 29

9/  271 - [(-43) + 271 - (-17)]

= 271 - [(-43) + 271 + 17]

= 271 + 43 - 271 - 17

= (271 - 271) + 43 - 17 = 26

10/ -144 - [29 - (+ 144) - (+144)]

= - 144 - [29 - 144 - 144]

= -144 - 29 + 144 + 144

= (- 144 + 144) - 29 + 144

= 115

XONG RỒI NHÌN SỐ MUỐN ĐAU MẮT !!!!!!!!!!!!!!!!!!!!!!

1: 8=2^3

2: 25=5^2

3: 4=2^2

4: 49=7^2

5: 81=9^2

6: 36=6^2

7: 100=10^2

8: 121=11^2

9: 144=12^2

10: 169=13^2

11: 27=3^3

12: 125=5^3

13: 1000=10^3

14: 32=2^5

15: 243=3^5

16: 343=7^3

17: 216=6^3

18: 64=4^3

19: 225=15^2

20: 128=2^7