Consider two sets A = \x Z : |(|x - 3| - 3)| 1\ and B = \x R - \1, 2\ : (x - 2)(x - 4)x - 1 e(|x - 2|) = 0 \. Then the number of onto functions f : A B is equal to :
- 32
- 81
- 79
- 62
Answer
(4) 62
Solution
Set A: -1 |x - 3| - 3 1
2 |x - 3| 4
x - 3 [-4, -2] [2, 4]
x [-1, 1] [5, 7]
A = \-1, 0, 1, 5, 6, 7\, n(A) = 6
Set B (x 1, 2): either (x - 2)(x - 4) = 0 x = 4 (x = 2 excluded)
or e|x - 2| = 0 |x - 2| = 1 x = 3 (x = 1 excluded)
B = \3, 4\, n(B) = 2
Onto functions from a 6-element set to a 2-element set = all functions − constant functions
= 26 - 2 = 62
Answer: (4)