Tính: a) 0,3 - 4/9 : 4/3 . 6/5 + 1 b) (-1/3)^2 -3/8 : (0,5)^3 -5/2. (-4) c) 1+2 : (2/3 - 1/6).(-2,25)

* Hướng dẫn giải

$$\begin{gathered} a) 0,3-\frac{4}{9}:\frac{4}{3}.\frac{6}{5}+1 \\ =(0,3+1)-\frac{4}{9}.\frac{3}{4}.\frac{6}{5} \\ =1,3-\frac{4.3.3.2}{3.3.4.5} \\ =1,3-\frac{2}{5}=\frac{13}{10}-\frac{2}{5} \\ =\frac{13}{10}-\frac{4}{10}=\frac{9}{10} \end{gathered}$$

$$\begin{gathered} b) {\left(\frac{-1}{3}\right)}^2-\frac{3}{8}:{(0,5)}^3-\frac{5}{2}.(-4) \\ =\frac{{(-1)}^2}{3^2}-\frac{3}{8}:0,125+\frac{5}{2}.4 \\ =\frac{1}{9}-\frac{3}{8}.8+10=\frac{1}{9}-3+10 \\ =\frac{1}{9}+(10-3)=\frac{1}{9}+7=\frac{64}{9} \end{gathered}$$

$$\begin{gathered} c) 1+2:\left(\frac{2}{3}-\frac{1}{6}\right).(-2,25) \\ =1+2:\left(\frac{4}{6}-\frac{1}{6}\right).\frac{-9}{4} \\ =1+2:\frac{1}{2}.\frac{-9}{4} \\ =1+2.2.\frac{-9}{4} \\ =1+4.\frac{-9}{4}\text{= 1 – 9 = – 8.} \end{gathered}$$

$$\begin{gathered} d) \left[\left(\frac{1}{4}-0,5\right).2+\frac{8}{3}\right]:2 \\ =\left[\left(\frac{1}{4}-\frac{1}{2}\right).2+\frac{8}{3}\right].\frac{1}{2} \\ =\left[\frac{-1}{4}.2+\frac{8}{3}\right].\frac{1}{2} \\ =\left[\frac{-1}{2}+\frac{8}{3}\right].\frac{1}{2} \\ =\left[\frac{-3}{6}+\frac{16}{6}\right].\frac{1}{2} \\ =\frac{13}{6}.\frac{1}{2}=\frac{13}{12} \end{gathered}$$