If the domain of the function f(x) = e ( 2x-35+4x ) + -1 ( 4+3x2-x ) is [ , ), then 2 + 4 is equal to
- 4
- 3
- 7
- 5
Answer
(1) 4
Solution
For e to be defined, 2x-35+4x > 0, which gives x < - 54 or x > 32 … (i)
For -1 we need -1 4+3x2-x 1, x 2.
4+3x2-x 1 ⇒ 4x+22-x 0 ⇒ x - 12 or x > 2
4+3x2-x -1 ⇒ 2x+62-x 0 ⇒ -3 x < 2
Taking both together, -3 x - 12 … (ii)
From (i) and (ii) the domain is [-3, - 54 ), so = -3 and = - 54.
∴ 2 + 4 = 9 - 5 = 4
Answer: (1)