What is the value of $ a^2 + b^2 +c^2 - 2ab =2bc +2 ca $ ?

(a - b - c)2 (a + b - c)2 (a + b + c)2 (a - b + c)2

(a - b + c)2

We know that,  (a + b + c)2 = a2 + b2 + c2  + 2ab + 2bc + 2ca (a - b + c)2 = a2 + b2 + c2 - 2ab - 2bc + 2ca