2) x³ при x=4; -5; 0,4; 2/3

Решение:

1. \( x^3 \) при \( x = 4 \): \( 4^3 = 64 \)
2. \( x^3 \) при \( x = -5 \): \( (-5)^3 = -125 \)
3. \( x^3 \) при \( x = 0.4 \): \( (0.4)^3 = 0.064 \)
4. \( x^3 \) при \( x = \frac{2}{3} \): \( (\frac{2}{3})^3 = \frac{8}{27} \)

Ответ: 64; -125; 0.064; \(\frac{8}{27}\).