Đáp án:
$c)\dfrac{31}{9}\\ d)\dfrac{479}{330}\\ e)-\dfrac{2410}{999}\\ h)\dfrac{173}{55}$
Giải thích các bước giải:
$c)3,(4)=3+0,(4)=3+\dfrac{4}{9}=\dfrac{27}{9}+\dfrac{4}{9}=\dfrac{27+4}{9}=\dfrac{31}{9}\\ d)1,4(51)\\ =1,4+0,0(51)\\ =\dfrac{14}{10}+0,(51).\dfrac{1}{10}\\ =\dfrac{14}{10}+\dfrac{51}{990}\\ =\dfrac{14.99}{990}+\dfrac{51}{990}\\ =\dfrac{1386+51}{990}\\ =\dfrac{1437}{990}\\ =\dfrac{479}{330}\\ e)-2,(412) \\ =-2-0,(412) \\ =-2-\dfrac{412}{999}\\ =-\dfrac{1998}{999}-\dfrac{412}{999}\\ =\dfrac{-1998-412}{999}\\ =-\dfrac{2410}{999}\\ h)3,1(45)\\ =3,1+0,0(45)\\ =\dfrac{31}{10}+0,(45).\dfrac{1}{10}\\ =\dfrac{31}{10}+\dfrac{45}{990}\\ =\dfrac{31.99+45}{990}\\ =\dfrac{3114}{990}\\ =\dfrac{173}{55}$
