## Intermediate Algebra (12th Edition)

Recall: (1) A direct variation is represented by the equation $y=kx$ or, in the case of a power of $x$, $y=kx^n$ where $k$ is the constant of variation. (2) An inverse variation is represented by the equation $y=\dfrac{k}{x}$ where $k$ is the constant of variation. (3) A joint variation between two variables is represented by the equation $y=kxz$ or, in the case of a power of $x$ and/or $z$, $y=kx^mz^n$ where $k$ is the constant of variation. Any combination of direct and inverse variations is called a combined variation. Notice that the given equation involves both direct (a variable on the numerator) and inverse variations (variable/s in the denominator). Thus, the given equation represents combined variation.