Question

Tính: 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56

Answer 1

\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+......+\frac{1}{56}\)

\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+......+\frac{1}{7.8}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+.....+\frac{1}{7}-\frac{1}{8}\)

\(=1-\frac{1}{8}\)

\(=\frac{7}{8}\)

Answer 2

tui bít

Answer 3

bang 7/8 nha chi 

Answer 4

bang 7/8 nha chi 

Answer 5

7/8 nha chi

Answer 6

1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8

=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8

=1/1-1/8

=8/8-1/8

=7/8

Answer 7

7/8 đó

Answer 8

\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\)\(+\frac{1}{42}+\frac{1}{56}\)

= \(\frac{7}{8}\)

Answer 9

ra 7/8 bài này dễ ợt

Answer 10

1/2+1/6+1/12+1/20+1/30+1/42+1/56

=1/1.2+1/2.3+1/3.4+1/4.5+1/5.6+1/6.7+1/7.8

=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8

=1-1/8=7/8

Answer 11

7/8 nha chị, chị nha, nha chị

Answer 12

\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{7}-\frac{1}{8}\)

\(=1-\frac{1}{8}\)

\(=\frac{7}{8}\)