Factorise each of the following:
a2 - (b - c)2
a2 - (b - c)2
a2 - (b - c)2 = {a + (b - c)}{a - (b - c)}
| Using Identity III
= (a + b - c)(a - b + c)
x2 + 7xy + 12y2
x2 + 7xy + 12y2 = x2 + 3xy + 4xy + 12y2
= x(x + 3y) + 4y(x + 3y)
= (x + 3y)(x + 4y)