Let [ ] denote the greatest integer function. If the domain of the function f(x)= -1 ( x+[x]3 ) is [ , ), then 2+ 2 is equal to :
- 2
- 5
- 10
- 13
Answer
(2) 5
Solution
-1t is defined only for -1 t 1
-1 x+[x]3 1 -3 x+[x] 3
Let x [n, n+1), n Z [x]=n and x+[x] [2n, 2n+1)
n=-2 : x+[x] [-4, -3), every value <-3 (rejected)
n=-1 : [-2, -1); n=0 : [0, 1); n=1 : [2, 3) (all allowed)
n=2 : [4, 5), every value >3 (rejected)
Domain =[-1, 0) [0, 1) [1, 2)=[-1, 2)
=-1, =2
2+ 2=1+4=5
Answer: (2)