(i) (x + 3) (x + 7)

= x^{2} + (3 + 7) x + (3) (7)

= x^{2} + 10x + 21

(ii) (4x + 5) (4x + 1)

= (4x)^{2} + (5 + 1) (4x) + (5) (1)

= 16x^{2} + 24x + 5

(iii) (4x - 5) (4x - 1)

= (4x)^{2} + [ (-5) + (-1) ] (4x) + (5) (-1)

= 16x^{2} + 16x -5

(iv) (4x + 5) (4x - 1)

= (4x)^{2} + [ (5) + (-1) ] (4x) + (5) (-1)

=16x^{2} + 16x − 5