All functions are relations but not all relations depict functions. To determine whether a relation represented in ordered pairs and table of values a function or not, just observe its x-values. If there is no repetition on the x- values, then it's a function otherwise, it is not. If the relation is expressed in mapping diagram, the one-to-one and many-to-one correspondence only illustrate a function. The one-to-many and many-to- many are not. The relations when expressed in equation/rule, for every specific value of x, there should only be one corresponding y-value for that x-value. For example, y = x + 10, is a function because y will always be ten greater than x. Equations with exponents can also be functions. For example, y=x2-4 is a function; although x- values of 2 and -2 give the same y-value of zero (0), that is only possible y-value for each of those x-values. However, y2x 1 is not a function because if you assign x-value of 8, y has two possible values which are 3 and -3. Expressing it in ordered pairs, (8, 3) and (8, -3). Looking at these ordered pairs, there is a repeated value in x​