1/1.2+1/2.3+1/3.4+...+1/999.1000+1
=1-1/2+1/2-1/3+1/3-1/4+...+1/998-1/999+1/999-1/1000+1
=1-1/1000+1
=999/1000+1
=1999/1000
Chuẩn ko cần chỉnh
\(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{999\times1000}+1\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{999}-\frac{1}{1000}+1\)
\(=1-\frac{1}{1000}+1\)
\(=\frac{999}{1000}+1\)
\(=\frac{1999}{1000}\)
=1-1/2+1/2-1`/3+1/3-1/4+......+1/999-1/1000+1
=1-1/1000+1
=1999/1000
đúng thì kick nha !
=\(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+.....+\frac{1}{999}-\frac{1}{1000}+1\) =\(1-\frac{1}{1000}+1\) =\(\frac{1999}{1000}\)
