SO SÁNH A= 20052005 +1/20052006+1 và B =20052004+1/20052005+ 1
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Bài 1. Rút gọn các phân số:
24/36 =2/3
12/81=4/27
125/250 =1/2
131313/151515=13/15
20052005/20062006= 2005/2006
Bài 2: So sánh các phân số sau;
3/8 và 1/3
Ta có: 3/8 = 9/24 ; 1/3 = 8/24
=> 3/8 > 1/3
2/5 và 4/7
Ta có: 2/5 = 14/35 ; 4/7 = 20/35
=> 2/5 < 4/7
2004/2005 và 2005/2006
Ta có: 2004/2005 = 1 - 2004/2005 = 1/2005
2005/2006 = 1 - 2005/2006 = 1/2006
=> 2004/2005 < 2005/2006
Bài 4 Tim y biết:
y : 2 + y + y : 3 + y : 4 = 25
=> y : 2 + y : 1 + y : 3 + y : 4 = 25
=> y : (2+1+3+4)=25
=> y : 10 = 25
=> y = 25 x 10
=> y = 250
Vậy y=250
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151515 X 40104010 / 20052005 X 464646 = 15 / 23
1751/2575 = 17/25
Tìm Phân số trung gian :
15/23 = 1-15/23 = 8/23 17/25 = 1-8/25
Vì 8/23 > 8 /25 Nên 15/23 < 17/25 Vậy 151515 X 40104010 / 20052005 X 464646 < 1751/2575
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= - 4 020 023 < âm nha bn >
~~ tk mk đi ~~
Ai tk mk mk tk lại ~~ ^^
ai kb vs mk ik ~~ n_n
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\(\left(\frac{20052005}{20062006}-\frac{20042004}{20052005}\right)\cdot2005\cdot2006\)
=\(\left(\frac{2005\cdot10001}{2006\cdot10001}-\frac{2004\cdot10001}{2005\cdot10001}\right)\cdot2005\cdot2006\)
=\(\frac{2005\cdot2005\cdot2006}{2006}-\frac{2004\cdot2005\cdot2006}{2005}\)
= \(2005\cdot2005-2004\cdot2006\)
=\(2005^2-\left(2005-1\right)\cdot\left(2005+1\right)\)
=\(2005^2-2005^2+1\)
=1
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a, \(\frac{1}{2009}+\frac{2}{2009}+...+\frac{2008}{2009}\\ \frac{\left(1+2008\right)\cdot2008\div2}{2009}=\frac{2017036}{2009}\)
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M = N
vì: 20052005 < 200520052005 nhưng 200620062006 > 20062006
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Ta rút gọn hai phân số rồi so sánh:
\(\frac{200420042004}{200520052005}\) = \(\frac{200420042004:100010001}{200520052005:100010001}\) = \(\frac{2004}{2005}\)
\(\frac{20042004}{20052005}\) = \(\frac{20042004:10001}{20052005:10001}\)= \(\frac{2004}{2005}\)
Ta thấy: \(\frac{2004}{2005}\)= \(\frac{2004}{2005}\)
Vậy: hai phân số này bằng nhau
ta có:
\(\frac{200420042004}{200520052005}=\frac{200420042004:100010001}{200520052005:100010001}=\frac{2004}{2005}\)
\(\frac{20042004}{20052005}=\frac{20042004:10001}{20052005:10001}=\frac{2004}{2005}\)
\(\Rightarrow\frac{200420042004}{200520052005}=\frac{20042004}{20052005}\)
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(20052005/20062006-20042004/20052005)x2005/2006
=(2005x10001/2006x10001-2004x10001/2005x10001)x2005/2006
=(2005/2006-2004/2005)x2005/2006
=((2005x2005-2004x2006)/2006x2005)x2005/2006
=((2004x2005+2005-2004x2005+2004)/2005x2006)x2005/2006
=(1/2005x2006)x2005/2006
=2005/2005x2006x2006
=1/2006x2006=1/4024036
chúc bạn học tốt nha :)
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Xét A trước ta có
\(A=\frac{2005^{2005}+1}{2005^{2006}+1}\)ta có \(2005.A=\frac{2005.\left(2005^{2005}+1\right)}{2005^{2006}+1}\)
\(2005A=\frac{2005^{2006}+2005}{2005^{2006}+1}\)\(2005A=\frac{2005^{2006}+1+2004}{2005^{2006}+1}\)
\(2005.A=1+\frac{2004}{2005^{2006}+1}\)
Xét B ta có
\(B=\frac{2005^{2004}+1}{2005^{2005}+1}\)ta có \(2005B=\frac{2005\left(2005^{2004}+1\right)}{2005^{2005}+1}\)
\(2005B=\frac{2005^{2005}+2005}{2005^{2005}+1}\)\(2005B=\frac{2005^{2005}+1+2004}{2005^{2005}+1}\)
\(2005B=1+\frac{2004}{2005^{2005}+1}\)
ta có vì 2005A<2005B
từ đó suy ra A<B
nhớ **** đó