Factorise.
(i) `x^2 + xy + 8x + 8y`
(ii) `15xy - 6x + 5y - 2`
(iii) `ax + bx - ay - by`
(iv) `15pq + 15 + 9q + 25p`
(v) `z - 7 + 7xy - xyz`

Explanation

(i) `x^2 + xy + 8x + 8y`

`= x(x+y) + 8(x+y) `

`= (x+y)(x+8) `

(ii) `15xy - 6x +5y - 2`

`= 5y(3x+1) -2(3x+1)`

`= (5y-2)(3x+1)`

(iii) `ax+bx-ay-by`

`a(x-y) + b(x-y)`

...