To find if a relation is a function, identify if there is more that one value of y for the same value of x (if there are more than one value for one value of x is not a function)
Ordered pairs (x,y)
1.
x y
1 -2
-2 0
-1 2
1 3
As there are two values of y when x=1. (1 , -2) and (1 ,3). The relation is not a function2.
x y
1 1
2 2
3 5
4 10
5 15
As there are no more than one value of y for the same value of x. The relation is a function.