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Bùi Thùy Linh
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Tẫn
4 tháng 11 2018 lúc 9:54

\(A=13!-11!=1.2.3.4.5.6.7.8.9.10.11.12.13-1.2.3.4.5.6.7.8.9.10.11\)

a) \(13!⋮2\)\(11!⋮2\)\(\Rightarrow A⋮2\)

b) \(13!⋮5\)\(11!⋮5\)\(\Rightarrow A⋮5\)

c) \(A=13!-11!=1.2.3.4.5.6.7.8.9.10.11.12.13-1.2.3.4.5.6.7.8.9.10.11\)

\(=1.2.3.4.5.6.7.8.9.10.11.\left(12.13-1\right)\)

\(=1.2.3.4.5.6.7.8.9.10.11.155\)

\(\text{​​}\Rightarrow A⋮155\)

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Hoa Hồng Xanh Bất Tử
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dung51ngt
5 tháng 7 2016 lúc 17:32

a) có

b) có

c) có

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dung51ngt
5 tháng 7 2016 lúc 17:33

a) có

b) có

c) có 

k mình nha

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ánh ngọc
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big band
1 tháng 11 2015 lúc 16:59

*13! chia hết cho 2

11! chia het cho 2=>13!-11! chia hết cho 2

*13! chia het cho 5

11! chia het cho 5=>3!-11! chia het cho 5

*155=5.31

13! ko chia hết cho 5.31

11! ko chia het cho 5.31=>13!-11! ko chia het cho 155

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big band
1 tháng 11 2015 lúc 16:47

a)A chia hết cho 2

b)A chia hết cho 5

c)A ko chia het cho 155

**** GIÙM MÌNH NHA

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nguyen phan ha vi
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Trần Thị Loan
14 tháng 10 2015 lúc 16:40

a) 13! = 13.12.11....5.4.3.2.1 => 13! chia hết cho 2 và 5

11! = 11.10.9....5.4.3.2.1 => 11! chia hết cho 2 và 5

=> A = 13! - 11! chia hết cho 2 và 5

c) A = 13! - 11! = 13.12.11! - 11! = (13.12 - 1) .11! = 155.11! chia hết cho 155

Vậy A chia hết cho 155

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hoàng minh đức
18 tháng 10 2017 lúc 21:58

cảm ơn Trần Thị

 Loan nhé

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luuphidinh
17 tháng 1 2018 lúc 20:02

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Trần Thị Hà Giang
30 tháng 9 2018 lúc 10:39

 \(A=13!-11!\)

\(A=11!\cdot12\cdot13-11!\)

\(A=11!\left(12\cdot13-1\right)\)

\(A=11!\cdot155\)

\(\Rightarrow\)A chia hết cho 2 ( vì trong 11! chứa thừa số 2 )

         A chia hết cho 5

         A chia hết cho 155

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Kaito Kuroba_Kaito Kid
12 tháng 10 2018 lúc 10:31

a)A có chia hết cho 2

b)A có chia hết cho 5

c)A có chia hết cho 155

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jim
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Vũ Huyền Nga
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Đoàn Thị Việt Trang
27 tháng 11 2016 lúc 19:38

a) 13! = 13.12.11.....5.4.3.2.1 => 13! chia hết cho 2 và 5

11! = 11.10.9.....5.4.3.2.1 =>11! chia hết cho 2 và 5

=> A chia hết cho 2 và 5

c) A = 13! - 11! = 13.12.11! - 11! = ( 13.12 - 1 ) .11! = 155. 11! chia hết cho 155

Vậy A chia hết cho 155

Phần b) và a) mk gộp vào rồi nhé. Duyệt nha bạn . Chúc bạn học tốt

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Son Nguyen Cong
27 tháng 11 2016 lúc 19:40

Ta có:

 A = 13! -11!

    = 11!(12.13-1)

    = 11! . 155

Mà 11! chia hết cho 2, 5 nên A chia hết cho 2 và 5.

Mà 155 chia hết cho 155 nên A chia hết cho 155

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Trần Nguyễn Thúy Hạnh
30 tháng 11 2017 lúc 20:17

A = 13! - 11! = 1 . 2 . 3 . 4 . ...... . 13 - 1 . 2 . 3 . 4 . .... . 11

                    = 1 . 2 . 3 . 4 . .... . 11 ( 12 . 13 - 1 )

                    = 1 . 2 . 3 . 4 . .... . 11 ( 156 - 1 )

                    = 1 . 2 . 3 . 4 . .... . 11 . 155

    vì tích trên có chứa thừa số 2 ; 5 ; 155

=> A chia hết cho 2 ; cho 5 ; cho 155

chúc bạn học giỏi

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Nguyễn Thiên Quỳnh
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trịnh lâm anh
18 tháng 8 2017 lúc 19:36

70.a,nếu n chẵn thì n+10 chẵn chia hết cho 2,nếu n lẻ thì n+15 chẵn chia hết cho 2(vì bất kì một số nào nhân với số chẵn đều ra số chẵn)

làm tương tự vậy là được thui 

A=13!-11!=11!.(12.13-1)=11!.155=1.2.3.4.5.....11.155

vì trong tích có các thừa soos2,5,155 nên  A chia hết cho 2,5,155

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Nguyễn Thiên Quỳnh
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l҉o҉n҉g҉ d҉z҉
18 tháng 8 2017 lúc 20:30

Vì n là số tự nhiên nên sảy ra 2 trường hợp

+ n là số chẵn thì n có dạng 2a 

Thay n = 2a ta có : (n + 10) ( n + 15) = (2a + 10)(n + 15)

                                                          = 2(a + 5)(n + 15) chia hết cho 2 

+ n là số lẻ thì n có dạng 2a + 1 

Thay n = 2a + 1 ta có : (n + 10)(n + 15) = (2a + 11)(2a + 16)

                                                             = 2(2a + 11)(a + 8) chia hết cho 2 

Vậy với mọi số tự nhiên n thì (n + 10)(n + 15) chia hết cho 2 (đpcm)

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