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A=(2009+2009^2)+(2009^3+2009^4)+...+(2009^9+2009^10)
A=[2009.(1+2009)]+[2009^3.(1+2009)]+....+[2009^9.(1+2009)]
A=2009.2010+2009^3.2010+...+2009^9.2010
A=2010(2009+2009^3+2009^5+......+2009^9) chia het cho 2010
Ta có :
\(A=2009+2009^2+2009^3+2009^4+....+2009^{10}\)
Tổng A có số số hạng là :
( 10 - 1 ) : 1 + 1 = 10 ( số hạng )
Vì \(10⋮2\)nên khi ta nhóm 2 số liên tiếp lại thành một căp thì không thừa số nào cả
\(\Rightarrow A=\left(2009+2009^2\right)+\left(2009^3+2009^4\right)+....+\left(2009^9+2009^{10}\right)\)
\(\Rightarrow A=2009.\left(1+2009\right)+2009^3.\left(1+2009\right)+....+2009^9.\left(1+2009\right)\)
\(\Rightarrow A=2009.2010+2009^3.2010+....+2009^9.2010\)
\(\Rightarrow A=2010.\left(2009+2009^3+....+2009^9\right)\)
Vì \(2009+2009^3+....+2009^9\inℤ\)nên \(2010.\left(2009+2009^3+....+2009^9\right)\inℤ\)
Vì \(2010⋮2010\)nên \(A⋮2010\)
Vậy \(A=2009+2009^2+2009^3+....+2009^{10}⋮2010\left(ĐPCM\right)\)
\(A=\left(2010^{2009}+2009^{2009}\right)^{2010}\)
\(=\left(2010^{2009}+2009^{2009}\right)^{2009}\left(2010^{2009}+2009^{2009}\right)\)
\(>\left(2010^{2009}+2009^{2009}\right)^{2009}.2010^{2009}\)
\(=\left(2010.2010^{2009}+2010.2009^{2009}\right)^{2009}\)
\(>\left(2010.2010^{2009}+2009.2009^{2009}\right)^{2009}\)
\(=\left(2010^{2010}+2009^{2010}\right)^{2009}=B\)
Vậy \(A>B\)
Dạo này anh ít on lắm em có nhờ thì em kiếm kênh khác nhờ không thì phải đợi a on a mới làm được nhé
Dễ quá, thực hiện qui tắc bỏ dấu ngoặc được:
\(2009+2009^2+....+2009^{2009}-1-2009-...-2009^{2008}\)
\(=-1+\left(2009-2009\right)+\left(2009^2-2009^2\right)+...+\left(2009^{2008}-2009^{2008}\right)+2009^{2008}\)
\(=2009^{2008}-1\)
\(=\left(2009-1\right)\left(2009^{2007}+2009^{2008}+...+2009+1\right)\)
\(=2008\left(2009^{2007}+2009^{2008}+...+2009+1\right)\) chia hết cho 2008
=> ĐPCM
Chứng Minh Rằng: (2009+20092+20093+20094+...+20092009)-(1+2009+20092+20093+...+20092008) chia hết cho 2008.
Đặt A=2009+20092+20093+20094+...+20092009, B=1+2009+20092+20093+20094+...+20092008
Ta có:
+)A=2009+20092+20093+20094+...+20092009
2009A= 20092+20093+20094+...+20092010
2009A-A=(20092+20093+20094+...+20092010)-(2009+20092+20093+20094+...+20092009)
2008A=20092010- 2009
=> A=(20092010- 2009)/2008
=> A chia hết cho 2008.
B=1+2009+20092+20093+20094+...+20092008
2009B=2009+20092+20093+20094+...+20092010
2009B-B=(2009+20092+20093+20094+...+20092010)-(1+2009+20092+20093+20094+...+20092009)
2008B=20092010-1
=>B=(20092010-1)/2008
=>B chia hết cho 2008
=> A-B chia hết cho 2008.
=> ĐPCM
Đặt \(a=2010^{2009};b=2009^{2009}\)\(\left(a,b>0\right)\)
\(A=\left(a+b\right)^{2010}=\left(a+b\right)^{2009}.\left(a+b\right)\)
\(B=\left(a.2010+b.2009\right)^{2009}=\left[a+2009\left(a+b\right)\right]^{2009}\)
Chia A và B cho \(\left(a+b\right)^{2009}:\)
\(A=a+b;B=\dfrac{\left[a+2009\left(a+b\right)\right]^{2009}}{\left(a+b\right)^{2009}}\)\(=\left(\dfrac{a}{a+b}+2009\right)^{2009}\)
Dễ thấy A<B.
\(B=\left(2010^{2009}.2010+2009^{2009}.2009\right)^{2009}\)
\(B< \left(2010^{2009}.2010+2009^{2009}.2010\right)^{2009}\)
\(B< \left(2010^{2009}+2009^{2009}\right)^{2009}.2010^{2009}\)
\(B< \left(2010^{2009}+2009^{2009}\right)^{2009}.\left(2010^{2009}+2009^{2009}\right)\)
\(B< \left(2010^{2009}+2009^{2009}\right)^{2010}\)
\(\Rightarrow B< A\)
Do 20092010-2<20092011-2=>B<1
Theo đề bài ta có:
\(B=\frac{2009^{2010}-2}{2009^{2011}-2}<\frac{2009^{2010}-2+2011}{2009^{2011}-2+2011}=\frac{2009^{2010}+2009}{2009^{2011}+2009}\)\(=\frac{2009\left(1+2009^{2009}\right)}{2009\left(1+2009^{2010}\right)}\)
\(=\frac{2009^{2009}+1}{2009^{2010}+1}\)\(=A\)=>B<A
\(A=2009+2009^2+2009^3+...+2009^{10}\) (có 10 số hạng)
\(A=\left(2009+2009^2\right)+\left(2009^3+2009^4\right)+...+\left(2009^9+2009^{10}\right)\) (có 5 nhóm)
\(A=2009\left(1+2009\right)+2009^3\left(1+2009\right)+...+2009^9\left(1+2009\right)\)
\(A=2009.2010+2009^3.2010+...+2009^9.2010\)
\(A=2010\left(2009+2009^3+...+2009^9\right)\)
Ta thấy: \(2010\left(2009+2009^3+...+2009^9\right)⋮2010\) (Vì \(2010⋮2010\) )
\(\Rightarrow A⋮2010\) (đpcm)
Vậy \(A⋮2010\)
A = (2009 + 20092 + 20093 + 20094 + .... + 200910)
A = [(2009 + 20092) + (20093 + 20094) + ... + (20099 + 200910)]
A = [4038090 + 20092(2009 + 20092) + ... + 20098(2009 + 20092)]
A = [4038090 + 20092.4038090 ... + 20098. 4038090] ⋮ 2010
(4038090 ⋮ 2010)