What is the difference between 126 1
/4
and 78 2
/3
?

cross multiplying, we get :

⇒ (3) × (5) = (9) × (x)

⇒ 15 = 9x

sample answer: you can determine whether each element of the domain is paired with exactly one element of the range. for example, if given a graph, you could use the vertical line test; if a vertical line intersects the graph more than once, then the relation that the graph represents is not a function.