Verified answer

4) 0,008x³ - 27y³ = (0,2x)³ - (3y)³ = (0,2x - 3y)(0,04x² + 0,6xy + 9y²)

5) (x - 5)² = 5x² - (2x - 1)(2x + 1)

x² - 10x + 25 = 5x² - (4x² - 1)

x² - 10x + 25 = 5x² - 4x² + 1

x² - 10x + 25 = x² + 1

x² - 10x - x² = 1 - 25

- 10x = - 24

x = 2,4