Question

Cách tính nhanh bài này là gì ???
A= [ 2/3 + 2/5 - 2/7 + 2/91] / [ 4/3 + 4/5 - 4/7 + 4/91]

Answer 1

\(A=\frac{\frac{2}{3}+\frac{2}{5}-\frac{2}{7}+\frac{2}{91}}{\frac{4}{3}+\frac{4}{5}-\frac{4}{7}+\frac{4}{91}}.\)

\(A=\frac{\frac{2}{3}+\frac{2}{5}-\frac{2}{7}+\frac{2}{91}}{2.\left(\frac{2}{3}+\frac{2}{5}-\frac{2}{7}+\frac{2}{91}\right)}\)

\(A=\frac{1}{2}\)

Answer 2

\(A=\frac{\frac{2}{3}+\frac{2}{5}-\frac{2}{7}+\frac{2}{91}}{\frac{4}{3}+\frac{4}{5}-\frac{4}{7}+\frac{4}{91}}=\frac{\frac{2}{3}+\frac{2}{5}-\frac{2}{7}+\frac{2}{91}}{2.\left(\frac{2}{3}+\frac{2}{5}-\frac{2}{7}+\frac{2}{91}\right)}=\frac{1}{2}\)

Cách này là nhanh nhất rùi

Ủng hộ mk nha ^_-

Answer 3

A=[2/3 + 2/5 - 2/7 + 2/91] / [4/3 + 4/5 - 4/7 +4/91]

  =[2/3 + 2/5 - 2/7 +2/91] / [2.(2/3 + 2/5 - 2/7 + 2/91]

  =                               1/2