The given expression is (3x + 2y)2 + (3x – 2y)2
We have,
(3x + 2y)2 = (3x)2 + 2.3x.2y + (2y)2(Here we apply standard identities)
= 9x2 + 12xy + 4y2
and
(3x-2y)2 = (3x)2-2.3x.2y + (2y)2
= 9x2-12xy + 4y2
Therefore,
(3x + 2y)2 + (3x – 2y)2 = 9x2 + 12xy + 4y2 + 9x2-12xy + 4y2
= 18x2 + 8y2
= 2(9x2 + 4y2)