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\(\frac{2007}{2008}\)\(+\)\(\frac{2008}{2009}\)\(=\)\(\frac{2007}{2008}\)\(+\)\(\frac{2008}{2009}\)
k mk nha!!! *o~
\(\frac{2007}{2008}+\frac{2008}{2009}=\frac{2007}{2008}+\frac{2008}{2009}\)
nha 
^_^
Có :\(a-b=\frac{2008}{2009}-\frac{2009}{2008}\)\(=\frac{2008^2-2009^2}{2008\cdot2009}=\frac{\left(2008-2009\right)\left(2008+2009\right)}{2008\cdot2009}\)
\(=\frac{-2008-2009}{2008\cdot2009}=-\frac{1}{2009}-\frac{1}{2008}\)
=>a-b+c+d=\(-\frac{1}{2009}-\frac{1}{2008}+\frac{1}{2009}+\frac{2007}{2008}\)
\(=-\frac{1}{2008}+\frac{2007}{2008}=\frac{2006}{2008}=\frac{1003}{1004}\)
a-b+c+d=\(\frac{2008}{2009}-\frac{2009}{2008}+\frac{1}{2009}+\frac{2007}{2008}=\left(\frac{2008}{2009}+\frac{1}{2009}\right)-\left(\frac{2009}{2008}-\frac{2007}{2008}\right)=1-\frac{2}{2008}=\frac{2006}{2008}=\frac{1003}{1004}\)
\(a-b+c+d=\frac{2008}{2009}-\frac{2009}{2008}+\frac{1}{2009}+\frac{2007}{2008}\)
\(=\left(\frac{2008}{2009}+\frac{1}{2009}\right)+\left(\frac{2007}{2008}-\frac{2009}{2008}\right)=\frac{2009}{2009}+\frac{-2}{2008}\)
\(=1+\frac{-1}{1004}=\frac{1004}{1004}+\frac{-1}{1004}=\frac{1003}{1004}\)
có : Q = [ 2 + 2^2 ] + [ 2^3 +2^4] + ... + [2^9 + 2^10]
Q = 2 [1+2] +2^3[1 +2]+ ...+ 2^9 [1+2]
Q = 2 . 3+2^3 .3 +... + 2^9 .3
Q = 3. [ 2 + 2^3 +... + 2^9]
Vậy Q chia hết cho 3
thế bài này bạn hỏi hay là tớ hỏi vậy
cậu chẳng ghi đề bài thì ai làm
\(=\left(\frac{2007}{2008}+\frac{1}{2008}\right)+\left(\frac{2007}{2008}.\frac{2008}{2009}+\frac{1}{2009}\right)\)
\(=1+\frac{2008}{2009}=\frac{4017}{2009}\)
\(\frac{2007}{2008}+\frac{1}{2009}+\frac{2007}{2008}:\frac{2009}{2008}+\frac{1}{2008}\)
\(=\frac{2007}{2008}+\frac{1}{2009}+\frac{2007}{2009}+\frac{1}{2008}\)
\(=\left(\frac{2007}{2008}+\frac{1}{2008}\right)+\left(\frac{2007}{2009}+\frac{1}{2009}\right)\)
\(=1+\frac{2008}{2009}\)
\(=\frac{4017}{2009}\)