2. Найдите значение выражения: a) 0,7 (0,2x - 1) + 0,7(0,4x - 5) при x=2\frac{1}{3}; б) \frac{4}{9}(y-3)-1\frac{5}{9}(6-y) при y = -0,9.

a) Найдем значение выражения: \[ 0.7(0.2x - 1) + 0.7(0.4x - 5) \] при x = 2\frac{1}{3} = \frac{7}{3} \[ 0.7\left(0.2 \cdot \frac{7}{3} - 1\right) + 0.7\left(0.4 \cdot \frac{7}{3} - 5\right) = 0.7\left(\frac{1.4}{3} - 1\right) + 0.7\left(\frac{2.8}{3} - 5\right) \] \[ = 0.7\left(\frac{1.4 - 3}{3}\right) + 0.7\left(\frac{2.8 - 15}{3}\right) = 0.7\left(-\frac{1.6}{3}\right) + 0.7\left(-\frac{12.2}{3}\right) \] \[ = -\frac{0.7 \cdot 1.6}{3} - \frac{0.7 \cdot 12.2}{3} = -\frac{1.12}{3} - \frac{8.54}{3} = -\frac{1.12 + 8.54}{3} = -\frac{9.66}{3} = -3.22 \]

б) Найдем значение выражения: \[ \frac{4}{9}(y - 3) - 1\frac{5}{9}(6 - y) \] при y = -0.9 \[ \frac{4}{9}(-0.9 - 3) - \frac{14}{9}(6 - (-0.9)) = \frac{4}{9}(-3.9) - \frac{14}{9}(6 + 0.9) \] \[ = \frac{4}{9}(-3.9) - \frac{14}{9}(6.9) = \frac{-15.6}{9} - \frac{96.6}{9} = \frac{-15.6 - 96.6}{9} = \frac{-112.2}{9} = -12.466... \]