1,3 1,5 1,7 1,9 is this a function. what is the domain and the range

No ... this is not a function because a function cannot have any repeating x values. They can have repeating y values, just not the x ones.

The domain is all the x values { 1 } ... if they are repeating, u only have to write it once.

The range is all the y values { 3,5,7,9}

f (x) = { (1,3), (1,5), (1,7), (1,9) }

Domain = 1, 1, 1, 1

Range = 3, 5, 7, 9