Factorise each of the following expressions:
(i) 48x³ - 36x²
(ii) 5x² - 15xy
(iii) 15x³y²z - 25xy²z³

6 If both (x + 1) and (x - 1) are factors of ax³ + x² - 2x + b, find a and b. 7 If x² - 1 is a factor of ax⁴ + bx³ + cx² + dx + e, show that a + c + e = b + d = 0. 9 Factorise
(i) 2x²(x + y) - 3(x + y) 
(ii) 5xy(5x + y) - 5y(5x + y)
(iii) x(x² + y² - z²) + y(x² + y² - z²) + z(x² + y²- z²)
(iv) ab(a² + b² - c²) + bc(a² + b² - c²) + ca(a²+b²-c²) 10 Factorise
(i) 6ab - b² + 12ac - 2bc
(ii) x² + y - xy - x
(iii) x³ - 2x²y + 3xy² - 6y³
(iv) a(a + b - c) – bc