Final answer:
The general formula for inverse variation is f = k/d where f varies inversely with d, and k is the constant of variation. As ƒ decreases, d increases and vice versa, keeping ƒ multiplied by d constant.
Step-by-step explanation:
The general formula to describe the variation when ƒ varies inversely with d is f = k/d, where k is the constant of variation. This means that as the value of ƒ decreases, d increases, and conversely, as ƒ increases, d decreases, maintaining the product of ƒ and d as a constant value.
To find the constant of proportionality (k), you would use a situation where you know the values of both f and d. Once the constant k is known, you can use the formula f = k/d to determine the value of f for any other value of d, and vice versa.