2) 3x³ + x² - 3х – 1, если х = 2\frac{2}{3}

2) $$3x^3 + x^2 - 3x - 1 = x^2(3x + 1) - (3x + 1) = (x^2 - 1)(3x+1)$$ Если $$x = 2\frac{2}{3} = \frac{8}{3}$$, то $$(x^2 - 1)(3x+1) = ((\frac{8}{3})^2 - 1)(3 \cdot \frac{8}{3} + 1) = (\frac{64}{9} - 1)(8 + 1) = (\frac{64}{9} - \frac{9}{9}) \cdot 9 = \frac{55}{9} \cdot 9 = 55$$ Ответ: 55