b: =-24+76=52

`4/7+4`

`=4/7+4/1`

`=4/7+28/7`

`=32/7`

__

`3+6/11`

`=33/11+6/11`

`=39/11`

__

`3-5/7`

`=3/1-5/7`

`=21/7-5/7`

`=16/7`

__

`21/9-2`

`=21/9-18/9`

`=3/9`

`=1/3`

__

`15/24+2`

`=15/24+48/24`

`=63/24`

`=21/16`

__

`63/45-20/25`

`=63/45-4/5`

`=63/45-36/45`

`=27/45`

`=9/15`

__

`3/4-2/8`

`=3/4-1/4`

`=2/4`

__

`6/7-5/8`

`=48/56-35/56`

`=13/56`

__

`37/45-5/9`

`=37/45-25/45`

`=12/45`

`=4/15`

__

`46/39-11/13`

`=46/39-33/39`

`=13/39`

`=1/2`

__

`5/12+3/4+1/3`

`=5/12+9/12+4/12`

`=14/12+4/12`

`=18/12`

`=3/2`

__

`1/2+3/7+11/14`

`=7/14+6/14+11/14`

`=13/14+11/14`

`=24/14`

`=12/7`

__

`7/10-(1/5+1/4)`

`=7/10-(4/20+5/20)`

`=7/10-9/20`

`=14/20-9/20`

`=5/20`

`=1/4`

__

`15/4-2/3-3/4`

`=(15/4-3/4)-2/3`

`=12/4-2/3`

`=3-2/3`

`=9/3-2/3`

`=7/3`

( - 63 ) . 39 + 37 . ( - 39 )                               Chúc bạn học tốt 

= - 63 . 39 + ( - 39 ) . 37

= - 63 .39 - 39 .37

= 39 . ( -63 - 37 )

= 39 . ( - 100 )

= - 3900

- 63 ) . 39 + 37 . ( - 39 )                               

= - 63 . 39 + ( - 39 ) . 37

= - 63 .39 - 39 .37

= 39 . ( -63 - 37 )

= 39 . ( - 100 ) = - 3900

77/120

27/28

\(\frac{39}{40}-\frac{7}{9}\div\frac{2}{3}\left(\times\frac{3}{2}\right)\times\frac{2}{7}\)\(=\frac{39}{40}-\frac{7\times3\times2}{3\times3\times2\times7}=\frac{39}{40}-\frac{1}{3}\)\(=\frac{117}{120}-\frac{40}{120}=\frac{77}{120}\)

-------------------------------------------------------------------------------------------------------------------------

\(\frac{20}{63}\div\frac{8}{9}\left(\times\frac{9}{8}\right)+\frac{5}{6}\times\frac{51}{70}=\frac{5\times4\times9}{9\times7\times4\times2}+\frac{5\times17\times3}{3\times2\times5\times14}\)\(=\frac{5}{14}+\frac{17}{28}=\frac{10+17}{28}=\frac{28}{28}=1\)

Nhận xét :

3 + 6 = 9

9 + 15 = 24

24 + 39 = 63 

63 + 102 = 165

Quy luận : Cứ lấy số đứng trước cộng số đứng sau thì ra số kế tiếp .

Vậy ta có:

102 + 165 = 267

267 + 165 = 432

432 + 267 = 699

699 + 432 = 1131

1131 + 699 = 1830

=> 5 số tiếp theo là :

267 , 432 , 699 , 1131 , 1830

Ta có dãy số : 3 , 6 ,9 , 15 , 24 , 39 , 63 , 102 , 165 ,267, 431 , 699 , 1131, 1830 ,......

trả lời câu hỏi :

3;6;9;15;24;39;63;102;165;267;432;699;1131;1830;...

K cho mình nha.

\(\frac{\frac{1}{9}-\frac{1}{39}+\frac{1}{63}}{\frac{1}{12}-\frac{1}{52}+\frac{1}{84}}=\frac{\frac{1}{3}\left(\frac{1}{3}-\frac{1}{13}+\frac{1}{21}\right)}{\frac{1}{4}\left(\frac{1}{3}-\frac{1}{13}+\frac{1}{21}\right)}=\frac{1}{3}:\frac{1}{4}=\frac{4}{3}\)

S, ĐK là x chia hết cho 3

B, ĐK là x chia hết cho 3

C, ĐK là x chia hết cho 3

20/36

\(\dfrac{20}{36}\)

Sửa đề:

24/(3×9) + 24/(9×15) + 24/(15×21) + ... + 24/(57×63)

= 24 × 1/6 × (1/3 - 1/9 + 1/9 - 1/15 + 1/15 - 1/21 + ... + 1/57 - 1/63)

= 4 × (1/3 - 1/63)

= 4 × 20/63

= 80/63

Chỗ \(\dfrac{24}{9\times5}\) là sao em nhỉ? đã đúng đề chưa thế em