Direct Variation

Direct variation describes a simple relationship between two variables. We say y varies directly with x if:

y = kx

for some constant k. (Some textbooks describe direction variation by saying that "y varies directly as x" or that "y is directly proportional to x.")

This means that as x increases, y increases and as x decreases, y decreases.

The graph of the direct variation equation is a straight line through the origin.

Direct Variation Equation for 3 different values of k