Let [.] denote the greatest integer function. Then - 2 2 ( 12(3 + [x])3 + [ x] + [ x] ) dx is equal to :
- 12 + 5
- 11 + 2
- 15 + 4
- 13 + 1
Answer
(2) 11 + 2
Solution
For - 2 < x < 0: -1 < x < 0, 0 < x < 1
[ x] = -1, [ x] = 0, denominator = 2
For 0 < x < 2: [ x] = 0, [ x] = 0, denominator = 3
Also [x] = -2 on (- 2, -1), -1 on (-1, 0), 0 on (0, 1), 1 on (1, 2)
I = - /2-1 12 12 dx + -10 12 22 dx + 01 12 33 dx + 1 /2 12 43 dx
= 6 ( 2 - 1 ) + 12 + 12 + 16 ( 2 - 1 )
= 22 ( 2 - 1 ) + 24
= 11 + 2
Answer: (2)