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

\(A=\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+.....+\frac{1}{132}\)

\(A=\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+.....+\frac{1}{11.12}\)

\(A=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+....+\frac{1}{11}-\frac{1}{12}\)

\(A=\frac{1}{5}-\frac{1}{12}\)

\(A=\frac{7}{60}\)

Answer 2

Ta có:

A = \(\frac{1}{5.6}\)+ \(\frac{1}{6.7}\)+\(\frac{1}{7.8}\)+\(\frac{1}{8.9}\)+\(\frac{1}{9.10}\)+\(\frac{1}{10.11}\)+\(\frac{1}{11.12}\)

Answer 3

A bằng 7/60

Answer 4

có :

A = \(\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}+\frac{1}{132}=\)\(\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}+\frac{1}{11.12}\)

A\(=\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}\)

A\(=\frac{1}{6}-\frac{1}{12}\)  \(=\frac{2}{12}-\frac{1}{12}=\frac{1}{12}\)

VẬY A=\(\frac{1}{12}\)

CHÚC BẠN HỌC GIỎI NHÉ!

Answer 5

Quên mất mk làm tiếp nka:

A = \(\frac{1}{5}\)- \(\frac{1}{6}\)+\(\frac{1}{6}\)- \(\frac{1}{7}\)+ \(\frac{1}{7}\)-\(\frac{1}{8}\)+ ...... + \(\frac{1}{11}\)- \(\frac{1}{12}\)

A  = \(\frac{1}{5}\)- \(\frac{1}{12}\)

A = \(\frac{7}{60}\) 

Answer 6

bạn nào chọn câu trả lời của tôi là sai z

nói cho biết

tôi trả lời đúng đó nha

Answer 7

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

=\(\frac{1}{5×6}+\frac{1}{6×7}+\frac{1}{7×8}+\frac{1}{8×9}+\frac{1}{9×10}+\frac{1}{10×11}+\frac{1}{11×12}\)

=\(\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}\)

=\(\frac{1}{5}-\frac{1}{12}\)

=\(\frac{7}{60}\)