Question
Expand the following:
(i) (x - 2y - 3z)2 (ii) 
Solution
(i) (x - 2y - 3z)2
= {(x) + (- 2y) + (- 3z)}2
= (x)2 + (- 2y)2 + (- 3z)2 +2(x) (- 2y) +2(-2y)(-3z)+2(-3z)(x)
= x2 + 4y2 + 9z2 - 4xy + 12yz - 6zx
= (x)2 + (- 2y)2 + (- 3z)2 +2(x) (- 2y) +2(-2y)(-3z)+2(-3z)(x)
= x2 + 4y2 + 9z2 - 4xy + 12yz - 6zx
