Factorise :

x² - y² - 2yz - z²

Factorise :

7a⁵ - 567a

Factorise xy² - xz², Hence, find the value of :

(i) 9 x 8² - 9 x 2²

(ii) 40 x 5.5² - 40 x 4.5²

Factorise :

(a - 3b)² - 36 b²