Question

BT1: Tính nhanh:

6) 81. \(\dfrac{12-\dfrac{12}{7}-\dfrac{12}{289}-\dfrac{12}{85}}{4-\dfrac{4}{7}-\dfrac{4}{289}-\dfrac{4}{85}}\) : \(\dfrac{5+\dfrac{5}{13}+\dfrac{5}{169}+\dfrac{5}{91}}{6+\dfrac{6}{13}+\dfrac{6}{169}+\dfrac{6}{91}}\). \(\dfrac{158158158}{711711711}\)

Answer 1

\(=81.\dfrac{12.\left(1-\dfrac{1}{7}-\dfrac{1}{289}-\dfrac{1}{85}\right)}{4.\left(1-\dfrac{1}{7}-\dfrac{1}{289}-\dfrac{1}{85}\right)}:\dfrac{5.\left(1+\dfrac{1}{13}+\dfrac{1}{169}+\dfrac{1}{91}\right)}{6.\left(1+\dfrac{1}{13}+\dfrac{1}{169}+\dfrac{1}{91}\right)}.\dfrac{158}{711}\)

\(=81.\dfrac{12}{4}:\dfrac{5}{6}.\dfrac{2}{9}\)

\(=243:\dfrac{5}{6}.\dfrac{2}{9}\)

\(=\dfrac{1458}{5}.\dfrac{2}{9}\)

\(=\dfrac{324}{5}\)