The given expression is
(1.5p + 1.2q)2 – (1.5p - 1.2q)2
We have
(1.5p + 1.2q)2 = (1.5p)2 + 2(1.5p)(1.2q) + (1.2q)2
and
(1.5p - 1.2q)2 = (1.5p)2-2(1.5p)(1.2q) + (1.2q)
Therefore,
(1.5p + 1.2q)2 – (1.5p - 1.2q)2
= (1.5p)2 + 2(1.5p)(1.2q) + (1.2q)2-(1.5p)2 + 2(1.5p)(1.2q)-(1.2q)2