If a = 7, b = 5, c = 3, then the value of a2 + b2 + c2 - ab - bc - ca is :
A. - 12
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
This Question Belongs to Arithmetic Ability >> Number System
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