Determine Whether the Relation Is Also a Function $\{ ( 1,9 ) , ( 2,7 ) , ( 4,6 ) , ( 8,6 ) , ( 10,6 ) \}$

Determine whether the relation is also a function.
- $\{ ( 1,9 ) , ( 2,7 ) , ( 4,6 ) , ( 8,6 ) , ( 10,6 ) \}$