CHO A=\(\frac{2008}{2009};b=\frac{2009}{2008};c=\frac{1}{2009};d=\frac{2007}{2008}\)
tính a - b + c + d
cho a>b>0. chứng minh rằng \(\frac{a^{2009}-b^{2009}}{a^{2009}+b^{2009}}>\frac{a^{2008}-b^{2008}}{a^{2008}+b^{2008}}\)
cho a =\(\frac{2008}{2009}\),b=\(\frac{2009}{2008}\),c=\(\frac{1}{2009}\),d=\(\frac{2007}{2008}\)tính a-b+c+d
\(a+b+c+d=\frac{2008}{2009}+\frac{2009}{2008}+\frac{1}{2009}+\frac{2007}{2008}\\ =\frac{2009}{2009}+\frac{4016}{2008}=1+2=3\)
so sánh 2 phân số : \(A=\frac{2008^{2009}+2}{2008^{2009}-1};B=\frac{2008^{2009}}{2008^{2009}-3}\)
Cho: a = \(\frac{2008}{2009}\) ; b = \(\frac{2009}{2008}\) ; c = \(\frac{1}{2009}\) ; d = \(\frac{2007}{2008}\)
Tìm : a - b+c+d
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=\(-\frac{1}{2009}-\frac{1}{2008}+\frac{1}{2009}+\frac{2007}{2008}\)
\(=-\frac{1}{2008}+\frac{2007}{2008}=\frac{2006}{2008}=\frac{1003}{1004}\)
so sánh 2008 với tổng 2009 số hạng sau\(s=\frac{2008+2007}{2009+2008}+\frac{^{2008^2+2007^2}}{2009^2+2008^2}+.....+\frac{2008^{2009}+2007^{2009}}{2009^{2009}+2008^{2009}}\)
Cho A là tổng các phân số viết theo quy luật :
\(A=\frac{2009}{2}+\frac{2008}{2^2}+\frac{2007}{2^3}+...+\frac{2}{2^{2008}}+\frac{1}{2^{2009}}\). Hãy chứng tỏ rằng: 2008 < A < 2009
So sánh : \(A=\frac{2008}{2009}+\frac{2009}{2010}+\frac{2010}{2011}vàB=\frac{2008+2009+2010}{2009+2010+2011}\)
Chứng minh rằng nếu a>b>0 thì \(\frac{a^{2009}-b^{2009}}{a^{2009}+b^{2009}}>\frac{a^{2008}-b^{2008}}{a^{2008}+b^{2008}}\)
tính nhanh : A= \(28\frac{7}{2008}+\frac{2008}{2009}+\frac{2001}{2008}+\frac{1}{2009}\)
\(A=28\left(\frac{7}{2008}+\frac{2001}{2008}\right)+\frac{2008}{2009}+\frac{1}{2009}=28+1+1=30\)
\(A=28\frac{7}{2008}+\frac{2008}{2009}+\frac{2001}{2008}+\frac{1}{2009}=\left(28+\frac{7}{2008}+\frac{2001}{2008}\right)+\left(\frac{2008}{2009}+\frac{1}{2009}\right)=29+1=30\)