Question

Identity (a-b) whole square

Answer 1

(a-b)^2 = a^2 + b^2 - 2ab

Answer 2

How this identity of (a - b)2 = a2 + b2 - 2ab is obtained: 

Taking LHS of the identity: 
(a - b)2 

This can also be written as: 
= (a - b) (a - b) 

Multiply as we do multiplication of two binomials and we get: 
= a(a - b) - b(a - b) 
= a2 - ab - ab + b2 

Add like terms and we get: 
= a2 - 2ab + b2 

Rearrange the terms and we get: 
= a2 + b2 - 2ab 

Hence, in this way we obtain the identity i.e. (a - b)2 = a2 + b2 - 2ab