Question

1/1.2+1/2.3+1/3.4+1/4.5+1/5.6

giai thich ro rang 

Answer 1

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)

\(=1-\frac{1}{6}\)

\(=\frac{5}{6}\)

Answer 2

Ta thấy: 1/1.2=1/1-1/2

              1/2.3=1/2-1/3

              .....

              1/5.6=1/5-1/6

=> 1/1.2+1/2.3+1/3.4+1/4.5+1/5.6=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6

=1/1-1/6

=5/6

      

Answer 3

\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)

\(=\frac{1}{1}-\frac{1}{6}=\frac{6}{6}-\frac{1}{6}=\frac{5}{6}\)

Answer 4

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}.\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{5}-\frac{1}{6}\)

\(=\frac{1}{1}-\frac{1}{6}\)

\(=\frac{5}{6}\)

Answer 5

giai thich ho,them 1 k