If a = 7, b = 5, c = 3, then the value of a² + b² + c² - ab - bc - ca is :

A. - 12

B. 0

C. 8

D. 12

Answer: Option D

Solution(By Examveda Team)

= (a² + b² + c² - ab - bc - ca)
= (a + b + c)² - 3 (ab + bc +ca)
= (7 + 5 + 3)² - 3 (35 + 15 + 21)
= (15)² - 3 × 71
= (225 - 213)
= 12