Let f(x) = 3 x - 2 + 4 - x be a real valued function. If and are respectively the minimum and the maximum values of f, then 2 + 2 2 is equal to
- 42
- 38
- 24
- 44
Answer
(1) 42
Solution
Domain: x - 2 0 and 4 - x 0, so x [2, 4].
Put x = 2 2 + 4 2 , [0, 2 ]; then x - 2 = 2 2 and 4 - x = 2 2
f = 3 2 + 2
Since a + b a2 + b2, the maximum is = 18 + 2 = 20 (reached at = 13, inside the interval).
The function rises to this maximum and then falls, so the minimum is at an end: f(0) = 3 2, f ( 2 ) = 2, hence = 2.
2 + 2 2 = 2 + 40 = 42
Answer: (1)