Find the value of a + b + c when ab + bc + ca = - 4 and a² + b² + c² = 17?
- 13
- 3
- 21
- None of these
Explanation
Given:
ab + bc + ca = -4
a² + b² + c² = 17
Using the identity (a + b + c)² = a² + b² + c² + 2(ab + bc + ca):
(a + b + c)² = 17 + 2(-4)
= 17 - 8
= 9
a + b + c = ±√9
= ±3
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