If the domain of the function f(x)= (0.6) ( | 2x-5x2-4 | ) is (- , a] \b\ [c, d) (e, ), then the value of a+b+c+d+e is .
Answer
4
Solution
f is defined when (0.6) | 2x-5x2-4 | 0.
∵ base 0.6<1: 0< | 2x-5x2-4 | 1, with x 2 and x 52
|2x-5| |x2-4|
(x2-4)2-(2x-5)2 0
(x2-2x+1)(x2+2x-9) 0
(x-1)2(x2+2x-9) 0
x=1 or x -1- 10 or x -1+ 10
(x= 2 are not in this set; -1+ 10 2.16< 52, so remove x= 52.)
Domain = (- ,-1- 10 ] \1\ [-1+ 10, 52 ) ( 52, )
a=-1- 10, b=1, c=-1+ 10, d=e= 52
∴ a+b+c+d+e=-1+1-1+5=4
Answer: 4