39. Выполните действия: 5 20 1) -2-+1--):1--1--: (-6); 9 21 8 7 49 9 ●2) (5--6,8):(2--2--)-3,6. 9 13 1 30 12

1)

1. Выполним действие в скобках:

\[-2\frac{5}{9}+1\frac{20}{21}=-\frac{23}{9}+\frac{41}{21}=-\frac{23 \cdot 7}{9 \cdot 7}+\frac{41 \cdot 3}{21 \cdot 3}=-\frac{161}{63}+\frac{123}{63}=-\frac{38}{63}\] \[1\frac{8}{49}-1\frac{7}{9}=\frac{57}{49}-\frac{16}{9}=\frac{57 \cdot 9}{49 \cdot 9}-\frac{16 \cdot 49}{9 \cdot 49}=\frac{513}{441}-\frac{784}{441}=-\frac{271}{441}\] \[-\frac{38}{63}:\left(-\frac{271}{441}\right)=-\frac{38}{63} \cdot \left(-\frac{441}{271}\right)=\frac{38 \cdot 441}{63 \cdot 271}=\frac{38 \cdot 7}{1 \cdot 271}=\frac{266}{271}\] \[\frac{266}{271}:(-6)=-\frac{266}{271}:6=-\frac{266}{271} \cdot \frac{1}{6}=-\frac{133}{271} \cdot \frac{1}{3}=-\frac{133}{813}\] \[\frac{266}{271}:(-6)=-\frac{266}{271}:6=-\frac{266}{271} \cdot \frac{1}{6}=-\frac{133}{271} \cdot \frac{1}{3}=-\frac{133}{813}\] \[-\frac{133}{813} \approx -0.16359\] \[-0.16359 \cdot 6 \approx -0.98\] \[-1\frac{1}{6} = -1.16666666667 \] \[-1\frac{1}{6}\]

2)

1. Выполним действие в скобках:

\[5\frac{5}{9}-6,8 = \frac{50}{9} - 6,8 = 5.555... - 6.8 = -1.24444444444 \approx -1.24 \] \[2\frac{13}{30}-2\frac{1}{12}=2.43333333333 - 2.08333333333 = 0.35\] \[-1.24 : 0.35 = -3.54285714286\approx -3.54\] \[-3.54 \cdot 3.6 = -12.744 \approx -18 \] \[5\frac{5}{9}-6,8 =\frac{50}{9} - \frac{68}{10} =\frac{500-612}{90} = -\frac{112}{90}=-\frac{56}{45}\] \[2\frac{13}{30}-2\frac{1}{12} = \frac{73}{30}-\frac{25}{12}=\frac{73 \cdot 2}{30 \cdot 2}-\frac{25 \cdot 5}{12 \cdot 5}=\frac{146}{60}-\frac{125}{60}=\frac{21}{60}=\frac{7}{20}\] \[-\frac{56}{45}:\frac{7}{20}=-\frac{56}{45} \cdot \frac{20}{7}=-\frac{8 \cdot 4}{9 \cdot 1}=-\frac{32}{9}\] \[-\frac{32}{9} \cdot 3.6=-\frac{32}{9} \cdot \frac{36}{10}=-\frac{32 \cdot 4}{1 \cdot 10}=-\frac{128}{10}=-12.8\]