# Application of Lines

## Vocabulary

### constant of proportionality

coefficient and nonzero constant $k$ in the direct variation equation $y=kx$

### dependent variable

variable, typically graphed on the $y$-axis, whose values depend on the values of the independent variable

### direct variation

relationship between two variables that can be written in the form:
$y=kx$

### independent variable

variable, typically graphed on the $x$-axis, whose values determine the values of the dependent variable

### rate of change

ratio that compares the amount of change in the dependent variable to the amount of change in the independent variable

### rise

vertical change between two points on a line

### run

horizontal change between two points on a line

### slope

ratio of the change in $y$ to the change in $x$ for two points on a line, represented as:
$\frac{\text{Rise}}{\text{Run}}$

### y-intercept

value of $y$ where a graph touches or crosses the $y$-axis