Question

\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\)

 

Answer 1

bài này dễ mà

Answer 2

1/2+1/6+1/12+1/20+1/30=1/1x2+1/2x3+1/3x4+1/4x5+1/5x6

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

                                    = 1-1/6

                                    = 5/6

Đúng thì k nha

Answer 3

\(\frac{1}{2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\)

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

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

Answer 4

Ta có: 1/2+1/6+1/12+1/20+1/30+1/42=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7=1-1/7=6/7

Answer 5

1/2+1/6 +1/12+1/20 + 1/30 = 1/1 x 2 + 1/2 x 3 + 1/3 x 4 + 1/4 x 5 + 1/5 x 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 6

1/2+1/6+1/12+1/20+1/30

=1/1x2+1/2x3+1/3x4+1/4x5+1/5x6

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

= 1-1/6

= 5/6

Answer 7

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

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

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

Answer 8

Theo bài ra , ta có :

1/2+1/6+1/12+1/20+1/30

=1/1x2+1/2x3+1/3x4+1/4x5+1/5x6

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

= 1-1/6

= 5/6