Question 84 (xi)
Simplify
(4.5a+1.5b)2+(4.5b+1.5a)2
We have, (4.5a+1.5b)2+(4.5b+1.5a)2
=(4.5a)2+(1.5b)2+2×4.5a×1.5b+(4.5b)2+(1.5a)2+2×4.5b×1.5a [using the identity, (a+b)2=a2+b2+2ab]
=20.25a2+2.25b2+13.5ab+20.25b2+2.25a2+13.5ab=22.5a2+22.5b2+27ab