Help me with topic of variation

Topic of variation is a mathematical concept that describes the relationship between two or more quantities. There are three main types of variation:

1. Direct Variation: One quantity varies directly as another if their ratio is constant. If y varies directly as x, then y = kx, where k is the constant of variation.

2. Inverse Variation: One quantity varies inversely as another if their product is constant. If y varies inversely as x, then y = k/x, where k is the constant of variation.

3. Joint Variation: One quantity varies jointly as two or more other quantities if it varies directly as the product of those quantities. If z varies jointly as x and y, then z = kxy, where k is the constant of variation.