Chapter 3: Problem 6
In Exercises \(5-36,\) graph the given functions. $$y=-2 x$$
Short Answer
Expert verified
Graph the line passing through (0, 0) and (1, -2).
Step by step solution
01
Identify the Function Type
The function given is \( y = -2x \). This is a linear function of the form \( y = mx + b \), where \( m \) is the slope and \( b \) is the y-intercept. Here, \( m = -2 \) and \( b = 0 \).
02
Determine the Slope and Y-Intercept
For the equation \( y = -2x \), the slope \( m \) is \(-2\) and the y-intercept \( b \) is \(0\). This means the line crosses the y-axis at (0, 0).
03
Plot the Y-Intercept
Begin plotting the graph by marking the y-intercept point at (0, 0) on the coordinate plane. This is where the line will cross the y-axis.
04
Use the Slope to Find Another Point
From the y-intercept (0, 0), use the slope to find another point. The slope of \(-2\) indicates a change of -2 in \( y \) for every +1 change in \( x \). From (0, 0), move 1 unit right (to x = 1) and 2 units down (to y = -2) to get the point (1, -2).
05
Draw the Line
With the two points, (0, 0) and (1, -2), plotted on the graph, draw a straight line through these points, extending the line across the grid.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
The slope-intercept form is a standardized way to write the equation of a straight line, given by the formula \( y = mx + b \). Here, \( m \) represents the slope of the line, and \( b \) denotes the y-intercept, which is where the line crosses the y-axis. This form is especially helpful when graphing a line because it directly provides you with two important pieces of information about the line's geometry.
- **Slope (\( m \))**: The slope tells you the angle or steepness of the line. A positive slope means the line ascends from left to right, while a negative slope means it descends. In the equation \( y = -2x \), the slope \( m \) is -2, indicating that for every 1 unit you move right along the x-axis, you move 2 units down.
- **Y-Intercept (\( b \))**: The y-intercept is the point where the line crosses the y-axis (where \( x = 0 \)). In the equation \( y = -2x \), \( b \) is 0, hence the y-intercept is at the origin (0, 0).
Linear Equations
Linear equations, like \( y = -2x \), describe straight lines on the coordinate plane. These equations are called "linear" because their graphs form straight lines. Linear equations are typically solved to find the value of \( y \) for given values of \( x \) and follow a consistent pattern of addition and multiplication.
- **Form**: Most linear equations can be written in the form \( Ax + By = C \). However, the slope-intercept form \( y = mx + b \) is often easier for graphing.
- **Properties**: Every linear equation has a constant rate of change. This means that the difference in \( y \) divided by the difference in \( x \) (i.e., the slope) is always the same. For \( y = -2x \), the slope is constant at -2.
- **Applications**: Linear equations model a variety of real-world situations, such as predicting expenses or income based on a flat rate plus a variable amount that increases steadily over time.
Coordinate Plane
The coordinate plane, also known as the Cartesian plane, is a two-dimensional number line created by the intersection of a horizontal line, the x-axis, and a vertical line, the y-axis. Every point on this plane is identified by a pair of numerical coordinates (x, y), which corresponds to its position relative to the x and y axes.
- **Axes**: The x-axis runs horizontally, and the y-axis runs vertically. These axes divide the plane into four quadrants.
- **Plotting Points**: A point is plotted on the coordinate plane by identifying its x-coordinate along the x-axis and its y-coordinate parallel to the y-axis. In our example, the point (0, 0) is where the line \( y = -2x \) crosses the y-axis, and the point (1, -2) helps in defining the slope.
- **Graphing Lines**: After plotting two or more points of a linear equation, you can draw a line through these points to extend it across the plane. This line represents all solutions \( (x, y) \) that satisfy the equation.