Tính: a) 5 3/4.-8/9; b) 3 3/4:2 1/2 c) -9/5 :1,2 d) (1,7)2,03 : (1,7)2,021

* Hướng dẫn giải

$$\begin{gathered} a) 5\frac{3}{4}.\frac{-8}{9}=\frac{23}{4}.\frac{-8}{9}=\frac{-46}{9} \\ b) 3\frac{3}{4}:2\frac{1}{2}=\frac{15}{4}:\frac{5}{2} \\ =\frac{15}{4}.\frac{2}{5}=\frac{3.5.2}{2.2.5}=\frac{3}{2} \\ =\frac{-9}{5}.\frac{5}{6}=\frac{(-3).3.5}{5.3.2}=\frac{-3}{2} \\ c) \frac{{\displaystyle -9}}{{\displaystyle 5}}:1,2=\frac{{\displaystyle -9}}{{\displaystyle 5}}:\frac{{\displaystyle 6}}{{\displaystyle 5}} \\ d) (1,7)2 023 : (1,7)2 021 = (1,7)2 023 – 2 021 = (1,7)2 = 2,89. \end{gathered}$$