Q411
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
AnswerAnswer: Option D
Solution
Answer: Option D
Solution:
= (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