Đáp án:
a. $\dfrac{5}{3}$
b. $\dfrac{1228}{1443}$
Giải thích các bước giải:
a. $\dfrac{2}{7} + \dfrac{1}{9} + \dfrac{1}{7} + \dfrac{5}{9} + \dfrac{8}{14}$
$= (\dfrac{2}{7} + \dfrac{1}{7}) +(\dfrac{1}{9} + \dfrac{5}{9}) + \dfrac{4}{7}$
$= (\dfrac{3}{7} + \dfrac{4}{7}) + \dfrac{6}{9}$
$= 1 + \dfrac{2}{3} = 1\dfrac{2}{3} = \dfrac{5}{3}$
b. $\dfrac{2}{3} + \dfrac{4}{37} + \dfrac{5}{111} + \dfrac{266}{1443}$
$= \dfrac{2}{3} + (\dfrac{4.39}{37.39} + \dfrac{5.13}{111.13} + \dfrac{266}{1443})$
$= \dfrac{2}{3} + (\dfrac{156}{1443} + \dfrac{65}{1443} + \dfrac{266}{1443})$
$= \dfrac{2}{3} + \dfrac{487}{1443} = \dfrac{2.481}{3.481} + \dfrac{487}{1443}$
$= \dfrac{962}{1443} + \dfrac{266}{1443} = \dfrac{1228}{1443}$
