If the range of the function f(x) = 5-xx2-3x+2, x 1, 2, is (- , ] [ , ), then 2 + 2 is equal to :
- 188
- 192
- 190
- 194
Answer
(4) 194
Solution
Let y = 5-xx2-3x+2
yx2 + (1 - 3y)x + (2y - 5) = 0
(x = 1 and x = 2 never satisfy this equation, and y = 0 is given by x = 5.)
For real x (when y 0): (1 - 3y)2 - 4y(2y - 5) 0
y2 + 14y + 1 0
Roots: y = -7 4 3
y -7 - 4 3 or y -7 + 4 3
= -7 - 4 3, = -7 + 4 3
2 + 2 = ( + )2 - 2 = 196 - 2(49 - 48) = 194
Answer: (4)