Question

State whether the relationship between the variables in the table is a direct variation, an inverse variation, or neither. If it is a direct or inverse variation, write a function to model it.
x=3,9,13,20
y=9,27,39,60

I know it's direct but how do I write a function model to it?,

Answer 1

When y increases, x increases ⇒ Direct 

y = kx
when y = 9, x =3
9 = k(3)
9 = 3k
k = 3

therefore y = 3x