CMR: A=1.2.3...2012(1+\(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2012}⋮2012\))
CMR: A=1.2.3...2012(1+\(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2012}⋮2012\))
1. Cho A= 1.2.3...2012.\(\left(1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2012}\right)\)
CMR: A chia hết cho 2013
Chứng minh 1.2.3...2012. ( 1 +\(\frac{1}{2}\)+\(\frac{1}{3}\)+...+\(\frac{1}{2012}\)) chia hết cho 13
Cho B=1.2.3.....2012.(1+\(\frac{1}{2}\)+\(\frac{1}{3}\)+....+\(\frac{1}{2012}\))
CTR B\(⋮\)2013
Ta có : B = 1.2.3.....671......2012(1 + \(\frac{1}{2}+\frac{1}{3}+.......+\frac{1}{2012}\))
<=> B = 1.2.4........672......2012.2013((1 + \(\frac{1}{2}+\frac{1}{3}+.......+\frac{1}{2012}\)) chai hết cho 2013
B=1.2.3...2012.(\(1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2012}\))
Chung minh rang B chai het cho 2013
giờ để đúng rồi đó anh em
A có chia hết cho 3 không?
\(A=\frac{2012+\frac{2011}{2}+\frac{2010}{3}+\frac{2009}{4}+...+\frac{1}{2012}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2012}+\frac{1}{2013}}\)
Xét tử:
\(2012+\frac{2011}{2}+\frac{2010}{3}+\frac{2009}{4}+...+\frac{1}{2012}\)
= \(\left(1+\frac{2011}{2}\right)+\left(1+\frac{2010}{3}\right)+...+\left(1+\frac{1}{2012}\right)+1\)
= \(\frac{2013}{2}+\frac{2013}{3}+...+\frac{2013}{2012}+\frac{2013}{2013}\)
= \(2013\left(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2013}\right)\)
Thay vào ta có:
A = \(\frac{2013\left(\frac{1}{2}+\frac{1}{3}+....+\frac{1}{2013}\right)}{\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2013}}\)
=> A = 2013
Mà 2013 chia hết cho 3
=> A chia hết cho 3
\(A=\frac{2012+\frac{2011}{2}+\frac{2010}{3}+\frac{2009}{4}+...+\frac{1}{2012}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2012}+\frac{1}{2013}}\)
hỏi A có chia hết cho 3 hay ko ?
http://d.f24.photo.zdn.vn/upload/original/2016/02/14/10/03/3204324726_616688374_574_574.jpg
\(choA=\frac{2012+\frac{2011}{2}+\frac{2010}{3}+\frac{2009}{4}+...+\frac{1}{2012}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2012}+\frac{1}{2013}}.hỏiAchia3dưbaonhiêu\)
A=\(\frac{1+\frac{2011}{2}+1+\frac{2010}{3}+1+...+\frac{1}{2012}+1+1}{\frac{1}{2}+...+\frac{1}{2013}}\)
A=\(\frac{\frac{2013}{2}+\frac{2013}{3}+...+\frac{2013}{2012}+\frac{2013}{2013}}{\frac{1}{2}+...+\frac{1}{2013}}\)
A=\(\frac{2013\left(\frac{1}{2}+...+\frac{1}{2013}\right)}{\frac{1}{2}+...+\frac{1}{2013}}\)
A=2013
Mà 2013: 3 = 671
Vậy A : 3 dư 0 hay\(A⋮3\)
Tính giá trị biểu thức :
\(A=\frac{\frac{1}{2013}+\frac{2}{2012}+\frac{3}{2011}+...+\frac{2011}{3}+\frac{2012}{2}+\frac{2013}{1}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+...+\frac{1}{2012}+\frac{1}{2013}+\frac{1}{2014}}\)
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