Let the range of the function f(x) = 12 + 3x + 3x, x R be [a, b]. If and are respectively the A.M. and the G.M. of a and b, then is equal to
- 2
- 2
Answer
(3) 2
Solution
Since - 2 3x + 3x 2, the denominator lies in [2 - 2, 2 + 2].
So a = 12 + 2 and b = 12 - 2.
a + b = (2 - 2) + (2 + 2)4 - 2 = 2, so = 1
ab = 14 - 2 = 12, so = 1 2
= 2
Answer: (3)