Chapter 3: Problem 79
Graph equation. Solve for \(y\) first, when necessary. \(y=-2.5 x+5\)
Short Answer
Expert verified
Graph by plotting the points (0,5) and (2,0), then draw a line through them.
Step by step solution
01
Identifying the Equation
We are given the linear equation in the slope-intercept form: \(y = -2.5x + 5\) where \(y\) is already isolated. Therefore, there is no need to solve for \(y\) because it's already solved.
02
Understanding the Slope and Y-Intercept
The equation \(y = -2.5x + 5\) is in the slope-intercept form \(y = mx + b\). Here, \(m = -2.5\) represents the slope, and \(b = 5\) is the y-intercept. This means the graph will cross the y-axis at \(5\).
03
Plotting the Y-Intercept
Start by plotting the y-intercept on the graph. Since \(b = 5\), place a point on the y-axis at \( (0, 5) \).
04
Using the Slope to Plot the Next Point
The slope \(-2.5\) can be expressed as \(-\frac{5}{2}\), meaning a change of -5 units in the y-direction for a change of 2 units in the x-direction. From the point \((0,5)\), move 2 units to the right (positive x-direction) to \((2,?)\), then move 5 units down (negative y-direction) to \((2,0)\). Plot this second point at \((2,0)\).
05
Drawing the Line
Draw a straight line through the points \((0, 5)\) and \((2, 0)\). This is the graph of the equation \(y = -2.5x + 5\).
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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 of a linear equation is a powerful tool used in graphing linear equations. It's expressed as \( y = mx + b \), where "\(m\)" represents the slope and "\(b\)" is the y-intercept. This form is super convenient because it straightforwardly gives us the core details needed to graph a line: the slope and where the line intersects the y-axis.
- "\( m \)" tells us how steep the line is and its direction (whether it goes up or down).
- "\( b \)" helps us know exactly where to start drawing our line on the graph.
Y-Intercept
The y-intercept is the point where the line crosses the y-axis. In the equation \( y = mx + b \), it's represented by "\(b\)". This value is essential because it gives you the starting point for graphing your line. Let's break it down:- Since the y-axis runs vertically, the x-coordinate of this point is always zero.- For the equation \( y = -2.5x + 5 \), the y-intercept is at \((0, 5)\).This means you already have one reliable point on your graph. If you imagine the line, it starts touching the y-axis precisely at \((0, 5)\). It may seem like a small detail, but it's a fundamental piece that simplifies constructing the rest of your graph.
Plotting Points
Plotting points on a graph involves marking certain coordinates that the linear equation will pass through. To begin, use your y-intercept. You can then apply the slope to determine additional points.
- Start with the y-intercept point, given as \((0, b)\).
- For the equation \( y = -2.5x + 5 \), this is the point \((0, 5)\).
Slope Calculation
The slope of a line indicates the direction and steepness. It's determined from the equation in slope-intercept form by the coefficient "\(m\)". In the example \( y = -2.5x + 5 \):- The slope "\(m\)" is \(-2.5\). Slope can be rewritten as a fraction to show steps between points. For instance:- \(-2.5\) can be \(-\frac{5}{2}\) – meaning for every 2 units moved right, you descend 5 units.This allows precise movement between points on the graph:
- Start with your known point, like the y-intercept \((0, 5)\).
- From there, use the slope to move to your next point, which in this equation brings you to \((2, 0)\).