Chapter 5: Problem 33
Find the \(x\) -intercept and the \(y\) -intercept of the line with the given equation. Sketch the line using the intercepts. A calculator can be used to check the graph. $$y=3 x+6$$
Short Answer
Expert verified
The x-intercept is \((-2, 0)\) and the y-intercept is \((0, 6)\).
Step by step solution
01
Identify the Equation Form
The given equation is in the slope-intercept form, which is written as \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept. In this equation, \(y = 3x + 6\), the slope \(m = 3\) and the y-intercept \(b = 6\).
02
Find the Y-Intercept
To find the y-intercept, set \(x = 0\) in the equation. Substitute \(x = 0\) into \(y = 3x + 6\): \[ y = 3(0) + 6 = 6 \]So, the y-intercept is the point \((0, 6)\).
03
Find the X-Intercept
To find the x-intercept, set \(y = 0\) and solve for \(x\). Substitute \(y = 0\) into the equation:\[ 0 = 3x + 6 \]Subtract \(6\) from both sides:\[-6 = 3x \]Divide both sides by \(3\):\[ x = -2 \]The x-intercept is the point \((-2, 0)\).
04
Sketch the Line Using the Intercepts
Plot the intercepts on a coordinate plane: the y-intercept \((0, 6)\) and the x-intercept \((-2, 0)\). Draw a straight line through these two points, which extends in both directions. This line represents the graph of \(y = 3x + 6\).
05
Verify with a Calculator
Using a graphing calculator, enter the equation \(y = 3x + 6\) to display the graph. Ensure that the intercepts match the points \((0, 6)\) and \((-2, 0)\) that were calculated.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Slope-Intercept Form
Linear equations often appear in what is known as the slope-intercept form: \( y = mx + b \). This format allows us to quickly determine essential information about a line on a graph. In this equation:
- \( m \) represents the slope of the line, indicating how steep the line is and the direction it slants. If \( m \) is positive, the line increases; if negative, it decreases.
- \( b \) is the y-intercept. This is where the line crosses the y-axis.
X-Intercept
The x-intercept is the point where the line crosses the x-axis. At this point, the value of \( y \) is zero because the line has not moved up or down from this axis. To find the x-intercept of a line, we set \( y = 0 \) in the equation and solve for \( x \). For the equation \( y = 3x + 6 \):
- Set \( y = 0 \) which gives \( 0 = 3x + 6 \).
- Subtract 6 from both sides to get \( -6 = 3x \).
- Divide both sides by 3 to find \( x = -2 \).
Y-Intercept
Unlike the x-intercept, the y-intercept is where the line crosses the y-axis. At this point, \( x \) is zero because the line hasn't moved left or right from the axis. To identify the y-intercept, simply substitute \( x = 0 \) into the equation and solve for \( y \). In our example equation \( y = 3x + 6 \):
- Enter \( x = 0 \), resulting in the expression \( y = 3(0) + 6 \).
- Calculate to find \( y = 6 \).
Graphing a Line
Graphing a line using its intercepts is a straightforward yet effective method. A line is fully defined on a graph once two points are known. Here's how to sketch a line using intercepts:
- Begin by plotting the y-intercept. In our example, start at point \( (0, 6) \) on the graph.
- Plot the x-intercept, which for \( y = 3x + 6 \) is \( (-2, 0) \).
- Draw a straight line through these two plotted points, making sure to extend the line in both directions beyond the intercepts.