Chapter 3: Problem 7
Sketch the line passing through the point \((-4,2)\) with slope \(-1 / 4\).
Short Answer
Expert verified
The line is \( y = -\frac{1}{4}x + 1 \), passing through points like \((0, 1)\) and \((4, 0)\).
Step by step solution
01
Understand the slope-intercept form
The slope-intercept form of a line is given by the equation \( y = mx + b \), where \( m \) is the slope, and \( b \) is the y-intercept.
02
Identify the slope and point
From the problem, the slope \( m = -\frac{1}{4} \). The line passes through the point \((-4, 2)\). We will use this point to find the y-intercept \( b \).
03
Substitute into the slope-intercept formula
Substitute \( m = -\frac{1}{4} \) into the equation and use the point \((-4, 2)\) to solve for \( b \). Set up the equation: \( 2 = -\frac{1}{4}(-4) + b \).
04
Solve for the y-intercept \( b \)
Compute \(-\frac{1}{4}(-4) = 1\), then substitute back to get \( 2 = 1 + b \). Solve for \( b \) by subtracting 1 from both sides: \( b = 1 \).
05
Write the equation of the line
The equation of the line using the slope \(-\frac{1}{4}\) and y-intercept \( b = 1 \) is \( y = -\frac{1}{4}x + 1 \).
06
Plot the line
To sketch the line, start by plotting the y-intercept at \( (0, 1) \). From this point, use the slope, \( -\frac{1}{4} \), to determine the direction: move 4 units to the right and 1 unit down to get another point, \( (4, 0) \). Connect these points to sketch the line.
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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 one of the most straightforward ways to represent a linear equation, especially useful for graphing and understanding the behavior of the line. This form is given by:
- \( y = mx + b \)
- Here, \( m \) denotes the slope of the line, indicating both its steepness and direction.
- The \( b \) represents the y-intercept, which is where the line crosses the y-axis.
Linear Equations
Linear equations are equations that create straight lines when graphed in a coordinate plane. They play a fundamental role in algebra and analytic geometry. Here's why they're important:
- They have a constant rate of change, represented by the slope.
- They only include variables raised to the first power (no exponents).
- Their graph is always a straight line, which can be vertical, horizontal, or slanting.
Graphing a Line
Graphing a line involves translating the linear equation into a visual representation on the coordinate plane. Here's how you can do it in several efficient steps:
- Start by identifying the y-intercept \( b \) from the equation, as this gives your initial point on the graph at \((0, b)\).
- Use the slope \( m \), particularly if it is in the form of a fraction like \(-\frac{1}{4}\), to determine how the line moves across the plane. From the y-intercept, move according to the slope: go 4 units right and 1 unit down to locate a second point.
- With these two points marked on the graph, draw a straight line through them. This line is the graphical representation of your equation.