If a2 + b2 + c2 = 6.25
ab + bc + ca = 0.52
find a + b + c if a + b + c < 0
Answer & explanation
Correct answer: option 2
(a + b + c)2 = a2 + b2 + c2 + 2(ab + bc +ca)
(a + b + c)2 = 6.25 + 2×0.52
a + b + c =\(\sqrt {7.29}\) = 2.7
a + b + c = -2.7 (a + b + c < 0)