Bài 4:
a: Vì -16<-14<-12<-11<-9<-3<-1
nên \(-\dfrac{16}{17}< -\dfrac{14}{17}< -\dfrac{12}{17}< -\dfrac{11}{17}< -\dfrac{9}{17}< -\dfrac{3}{17}< -\dfrac{1}{17}\)
b: 2<3<4<7<8<9<11
=>\(\dfrac{5}{2}>\dfrac{5}{3}>\dfrac{5}{4}>\dfrac{5}{7}>\dfrac{5}{8}>\dfrac{5}{9}>\dfrac{5}{11}\)
=>\(-\dfrac{5}{2}< -\dfrac{5}{3}< -\dfrac{5}{4}< -\dfrac{5}{7}< -\dfrac{5}{8}< -\dfrac{5}{9}< -\dfrac{5}{11}\)
c: 37>33
=>\(\dfrac{14}{37}< \dfrac{14}{33}\)
=>\(-\dfrac{14}{33}< -\dfrac{14}{37}< 0\left(1\right)\)
\(\dfrac{17}{20}=\dfrac{17\cdot19}{20\cdot19}=\dfrac{323}{380};\dfrac{18}{19}=\dfrac{18\cdot20}{19\cdot20}=\dfrac{360}{380}\)
mà 323<360
nên \(0< \dfrac{17}{20}< \dfrac{18}{19}< 1\)
mà \(1=\dfrac{3}{3}< \dfrac{4}{3}\)
nên \(0< \dfrac{17}{20}< \dfrac{18}{19}< \dfrac{4}{3}\left(2\right)\)
Từ (1),(2) suy ra \(-\dfrac{14}{33}< -\dfrac{14}{37}< 0< \dfrac{17}{20}< \dfrac{18}{19}< \dfrac{4}{3}\)
Bài 5:
\(-\dfrac{1}{3}=\dfrac{-150}{450};\dfrac{4}{5}=\dfrac{4\cdot90}{5\cdot90}=\dfrac{360}{450}\)
=>Ba số hữu tỉ khác nhau lớn hơn -1/3 và nhỏ hơn 4/5 là:
\(-\dfrac{100}{450}=-\dfrac{2}{9};\dfrac{150}{450}=\dfrac{1}{3};\dfrac{270}{450}=\dfrac{3}{5}\)
