Let (a−b)2 denote the square of a difference.
a. (i) Rewrite (a−b)2 as a product of two identical binomials.
b. (ii) Expand the product obtained in part (i) and simplify it completely.
c. (iii) Hence or otherwise, establish the general identity for (a−b)2 in terms of a and b.
d. (iv) Verify the identity for a=9 and b=4 by computing both sides separately.