Question

let x = {1234} which of the following sets of ordered pairs is a function from x to x?

a. {(1,2),(2,3)(3,4)(2,2)}
b. {(1,1)(2,1)(3,1)(4,1)}
c.{(1,4)(2,3)(3,1)}
d.{(2,2)(3,3)(4,4)}

Answer 1

my answer is letter b because all inside the x is in there (1234)

Answer 2

is my answer correct?

Answer 3

Correct.
For the set to be a function,
1. all the points in the domain must be defined (1,2,3,4)
2. there cannot have more than one definition of the same point in the domain. This is also why a is rejected.