If a, b, c be three real numbers of the same sign then the value of ab+bc+ca lies in the interval
A
[3,∞)
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B
(3,∞)
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C
[2,∞)
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D
(−∞,3)
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Solution
The correct option is A[3,∞) Since a, b, c are of same sign, ab,bc,ca are all +ive.
Apply A.M. ≥ G.M. ∴E≥3[ab.bc.ca]13=3
therefore E lies in the interval [3,∞)