(i) x² + xy + 8x + 8y

Taking x as common in first two terms and 8 as common in next two terms

x(x + y) +8 (x + y)

= (x + y)(x + 8)

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

Taking 3x as common in first two terms and 1 as common in next two terms

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

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

(iii) ax + bx – ay - by

Taking a as common in ax and -ay and b as common in remaining two terms

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

= (a + b)(x - y)

(iv) 15pq + 15 + 9q + 25p

Taking 3q as common in 15pq and 9q and 5 as common in remaining two terms

3q(5p + 3) + 5 (5p + 3)

= (3q + 5)(5p + 3)

(v) z-7 + 7xy -xyz

Taking xy as common in 7xy and -xyz and 1 as common in remaining two terms

1(z - 7) - xy (z - 7)

= (1 – x y) (z - 7)