Question

Tính bằng cách thuận tiện nhất:

1/2x3 + 1/3x4 + 1/4x5 + 1/5x6

Answer 1

=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6

=1/2-1/6=1/3

Answer 2

\(\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}=\dfrac{1}{2}-\dfrac{1}{6}=\dfrac{3-1}{6}=\dfrac{2}{6}=\dfrac{1}{3}\)

Answer 3

1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6

=1/2-1/6

=3/6-1/6

=2/6=1/3

Answer 4

\(\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}\)

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

\(=\dfrac{1}{2}-\dfrac{1}{6}\)

\(=\dfrac{1}{3}\)

Answer 5

`1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6`

`=1/3`

Answer 6

=1/2 - 1/3 + 1/3 - 1/4 + 1/4 -1/5 - 1/6

= 1/2 - 1/6

= 1/3