Ребята, помогите!

Разложите на множители:

1) 12a²b³-18a⁵b²;

2) (b²-7) ²-b (b²-7) ;

3) 8x+8y-ax-ay;

4) 8m⁷-6v²n-12m⁵n³+9n⁴.

1)

12a²b³-18a⁵b² = 6a ²b² (2b-3a³) ;

2)

(b²-7) ²-b (b²-7) = (b ²-7) (b-7-b) = (b²-7) · (-7) = 7· (7-b²) ;

3)

8x+8y-ax-ay = 8 (x+y) - a (x+y) = (x+y) (8-a) ;

4)

8m⁷-6m²n-12m⁵n³+9n⁴ = (8m⁷-6m²n) - (12m⁵n³-9n⁴) =

= 2m² (4m⁵-3n) - 3n³ (4m⁵-3n) =

= (4m⁵-3n) (2m²-3n³).