Grade 8
Mathematics
Linear Functions
Study Guide: Parallel and Perpendicular Lines
Vocabulary
| Term | Description |
|---|---|
| Cartesian Plane | a two-dimensional plane divided into four quadrants using x- and y-axis |
| Slope | a ratio of the rate at which the dependent variable is changing versus the rate at which the independent variable is changing; frequently expressed as $\frac{RISE}{RUN}$, or $\frac{\textit{The change in y}}{\textit{The change in x}}$ |
| Parallel Lines | lines having the same slope and different y-intercepts. |
| Perpendicular Lines | lines having opposite and inverse slopes. |
| Oposite Number | numbers that are the exact same distance from zero, but on opposite sides of zero, such as $2$ and $-2$. ß |
| Inverse Number | numbers that when multiplied together equal 1, such as $ \frac{2}{1} \times \frac{1}{2} = 1$. Also called reciprocals. |
Parallel Lines
Lines that are parallel have the same slope and different y-intercepts.
The following equations are parallel. Plot them on a grid to see.
\begin{align} y &= 3x + 4 \\ y &= 3x \\ y &= 3x - 6 \end{align}
Perpendicular Lines
Lines that are perpendicular meet at 90 degree angles. Their slopes are always opposite and inverse.
The following equations are perpendicular. Plot them on a grid to see.
\begin{align} y &= 3x + 4 \\ y &= -\frac{1}{3}x \end{align}
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