For this case we have to define "y" directly with "x" when there is a constant of proportionality "k", such that:
[tex]y = kx[/tex]
This is known as direct variation.
On the other hand, if y varies inversely with x we have to:
[tex]y = \frac {k} {x}[/tex]
This is known as inverse variation.
Answer:
[tex]y = kx[/tex], direct variation
