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\(\left(1+\frac{1}{2}\right)\times\left(1+\frac{1}{3}\right)\times..........\times\left(1+\frac{1}{2005}\right)\)
=\(\frac{3}{2}\times\frac{4}{3}\times............\times\frac{2006}{2005}\)
=\(\frac{2006}{2}=1003\)
a)\(=\left(\dfrac{2}{2}+\dfrac{1}{2}\right)\times\left(\dfrac{3}{3}+\dfrac{1}{3}\right)\times...\times\left(\dfrac{2005}{2005}+\dfrac{1}{2005}\right)\)
\(=\dfrac{3}{2}\times\dfrac{4}{3}\times...\times\dfrac{2006}{2005}=\dfrac{2006}{2}=1003\)
b)\(=\left(\dfrac{2}{3}+\dfrac{1}{3}\right)\times\dfrac{1}{2}=\dfrac{3}{3}\times\dfrac{1}{2}=\dfrac{1}{2}\)
\(\left(1-\frac{1}{99}\right)\left(1-\frac{1}{100}\right).....\left(1-\frac{1}{2005}\right)\)
\(=\frac{98}{99}.\frac{99}{100}.....\frac{2004}{2005}=\frac{98}{2005}\)
1/1*2 + 1/2*3 + 1/3*4 + ... + 1/2005*2006
= 1- 1/2 + 1/2 - 1/3 + 1/3 -1 /4 + ...+1/2005 - 1/2006
= 1 - 1/2006
= 2005/2006
\(=\dfrac{3}{2}\times\dfrac{4}{3}\times...\times\dfrac{2006}{2005}\)
\(=\dfrac{2006}{2}=1003\)