Разложите на множители.

1) 7 х³ - 28 х

2) 5 а² - 10 ab + 5b²

3) x³ - 8

5) x³ - y³ - 5x (x² + xy + y²)

1) 7x³ - 28x = 7x (x² - 4) = 7x (x + 2) (x - 2)

2) 5a² - 10ab + 5b² = 5 (a² - 2ab + b²) = 5 (a - b) ² = 5 (a - b) (a - b)

3) x³ - 8 = x³ - 2³ = (x - 2) (x² + 2x + 4)

4) x³ - y³ - 5x (x² + xy + y²) = (x - y) (x² + xy + y²) - 5x (x² + xy + y²) =

= (x² + xy + y²) (x - y - 5x) = (x² + xy + y²) ( - 4x - y) = - (4x + y) (x² + xy + y²)

1) 7 х (х²-4) = 7 х (х-2) (х+2)

2) 5 (а²-2 ав+в²) = 5 (а-в) (а-в)