Chapter 7: Problem 45
Contains the point \((-1,3)\) and is perpendicular to the line \(2 x-y=4\)
Short Answer
Expert verified
The equation is \(y = -\frac{1}{2}x + \frac{5}{2}\).
Step by step solution
01
Determine the slope of the given line
First, we start by rewriting the equation of the given line in slope-intercept form, which is \(y = mx + b\) where \(m\) represents the slope. The given line equation is \(2x - y = 4\). Let's solve for \(y\).\[2x - y = 4\] \[- y = -2x + 4\]\[y = 2x - 4\]The slope \(m\) of the given line is \(2\).
02
Calculate the perpendicular slope
The perpendicular slope (\(m_\perp\)) is the negative reciprocal of the slope of the given line. Given that the slope of the line \(2x - y = 4\) is \(2\), the perpendicular slope becomes:\[m_\perp = -\frac{1}{m} = -\frac{1}{2}\]
03
Use the point-slope form to find the equation
With the perpendicular slope \(-\frac{1}{2}\) and the given point \((-1, 3)\), we use the point-slope formula, which is \(y - y_1 = m(x - x_1)\), to find the equation of the line. Substitute \(m = -\frac{1}{2}\), \(x_1 = -1\), and \(y_1 = 3\).\[y - 3 = -\frac{1}{2}(x + 1)\]
04
Simplify the equation
Now, simplify the equation obtained from the point-slope form to make it easier to interpret or describe:\[y - 3 = -\frac{1}{2}x - \frac{1}{2}\]\[y = -\frac{1}{2}x + 3 - \frac{1}{2}\]\[y = -\frac{1}{2}x + \frac{5}{2}\]
05
Present the final equation
Thus, the equation of the line that is perpendicular to \(2x - y = 4\) and passes through the point \((-1, 3)\) is:\[y = -\frac{1}{2}x + \frac{5}{2}\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Slope-Intercept Form
The slope-intercept form of a linear equation is a way to express the equation of a line. It's written as \(y = mx + b\), where \(m\) represents the slope of the line, and \(b\) is the y-intercept.
This form makes it easy to quickly graph a line or understand its direction and position on a graph.
- Slope \(m\): This value indicates the steepness of the line. A positive slope means the line rises as it moves from left to right, while a negative slope means it falls.
- Y-intercept \(b\): This is the point where the line crosses the y-axis.
This form makes it easy to quickly graph a line or understand its direction and position on a graph.
Utilizing the Point-Slope Form
The point-slope form is another useful way to express the equation of a line, especially when you know one point on the line and the slope. It’s expressed as \(y - y_1 = m(x - x_1)\).
\(y - 3 = -\frac{1}{2}(x + 1)\). From here, you can simplify into slope-intercept form or any other preferred format by distributing and solving for \(y\).
This can be particularly helpful for constructing lines without needing to solve for a y-intercept right away.
- \(m\): This is still the slope of the line.
- \((x_1, y_1)\): This is the known point on the line.
\(y - 3 = -\frac{1}{2}(x + 1)\). From here, you can simplify into slope-intercept form or any other preferred format by distributing and solving for \(y\).
This can be particularly helpful for constructing lines without needing to solve for a y-intercept right away.
The Concept of Negative Reciprocal
When two lines are perpendicular, their slopes have a unique relationship. Specifically, they are negative reciprocals of each other.To find the negative reciprocal:
This reciprocal relationship is key when determining the slope of a line perpendicular to a given line. It ensures the two lines intersect at a right angle, thus making understanding perpendicularity clearer and more defined in graphing.
- Take the original slope and invert the fraction. If the slope is an integer \(m\), think of it as \(\frac{m}{1}\) and flip it to \(\frac{1}{m}\).
- Change the sign. If the original slope is positive, the negative reciprocal is negative, and vice versa.
This reciprocal relationship is key when determining the slope of a line perpendicular to a given line. It ensures the two lines intersect at a right angle, thus making understanding perpendicularity clearer and more defined in graphing.