Final answer:
Joint variation is when a quantity varies directly or inversely with more than one other quantity. This relationship can be graphed as a curve for inverse variation and a straight line for direct variation.
Step-by-step explanation:
The concept described in the question is called joint variation. Joint variation occurs when a quantity varies directly or inversely with more than one other quantity.
For example, if we have an equation y = kx/z, where k is the constant of variation and x and z are the other quantities, then we have a joint variation relationship.
When joint variation is graphed, the result is a curve for inverse variation and a straight line for direct variation.