Question

\(A=\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}+\frac{1}{132}\)

Answer 1

Bạn xem lời giải của mình nhé:

Giải:

\(A=\frac{1}{30}+\frac{1}{42}+...+\frac{1}{132}\\ =\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+...+\frac{1}{11.12}\\ =\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+...+\frac{1}{11}-\frac{1}{12}\\ =\frac{1}{5}-\frac{1}{12}=\frac{12-5}{60}=\frac{7}{60}\)

Chúc bạn học tốt!

Answer 2

A=\(\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}+\frac{1}{11.12}\)
  =1/5 - 1/6+1/6 -1/7+1/7-1/8+....+1/11 - 1/12
  = 1/5 - 1/12
  =12/60 -5/60
  = 7/60

Answer 3

cảm ơn bn nha

 

Answer 4

<3

Answer 5

A=1/5.6+1/6.7+1/7.8+1/8.9+1/9.10+1/10.11+1/11.12

A=1/5 -1/6+1/6-1/7+...+1/11-1/12

A=1/5-1/12

A=7/60

tick nha !