4.21. Вычислите по действиям:

А) (-3.4 + 4) * (-1.6 - 0.9)
1) -3.4 + 4 = 0.6
2) -1.6 - 0.9 = -2.5
3) 0.6 * (-2.5) = -1.5

Ответ: -1.5

Б) (-0.8 - 0.5 + 2.1) * \(\frac{2}{5} - 1\)
1) -0.8 - 0.5 + 2.1 = 0.8
2) \(\frac{2}{5}\) - 1 = \(\frac{2}{5}\) - \(\frac{5}{5}\) = -\(\frac{3}{5}\) = -0.6
3) 0.8 * (-0.6) = -0.48

Ответ: -0.48