Show that
(a - b) (a +b) + (b - c) (b + c) + (c - a) (c + a) = 0
LHS = (a - b) (a +b) + (b - c) (b + c) + (c - a) (c + a)
= (a2 - b2) + (b2 - c2 ) + (c2 - a2)
= a2 - b2 +b2 - c2 + c2 - a2
= a2 - a2 + b2 - b2 + c2 - c2
= 0
Since, LHS = RHS
∴ (a - b) (a +b) + (b - c) (b + c) + (c - a) (c + a) = 0