\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{999\cdot1000}+1\)
\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{999}-\frac{1}{1000}+1\)
\(=1-\frac{1}{1000}+1\)
\(=\frac{999}{1000}+1=\frac{1999}{1000}\)
1/1*2 + 1/2*3 + 1/3*4 +................+1/999*1000 +1
=1/2 + 1/6 + 1/12 + ....................+1/999000 +1
=1-1/2 + 1/2-1/3 + 1/3-1/4 +...+ 1/999- 1/1000+1
=1- 1/1000+1
=999/1000+1
=1999/1000