Write an equation that expresses the following relationship. P varies directly with the square of D. In your equation, use K as the constant of proportionality.

P = K D^2

The equation that expresses the given relationship is:

P = K * D^2

To express the relationship "P varies directly with the square of D" using the constant of proportionality K, we can write the equation as:

P = K * D^2

In this equation, P represents the variable that is directly proportional to the square of D, and K is the constant of proportionality. The squared term D^2 indicates that D is being multiplied by itself (or raised to the power of 2) in order to establish a direct relationship with P.