Chapter 3: Problem 93
Find an equation of the perpendicular bisector of the line segment whose endpoints are given. \((-2,6) ;(-22,-4)\)
Short Answer
Expert verified
The equation of the perpendicular bisector is \(y = -2x - 23\).
Step by step solution
01
Calculate the Midpoint
To find the equation of the perpendicular bisector, we first need the midpoint of the line segment with endpoints \((-2,6)\) and \((-22,-4)\). The formula for the midpoint \((x_m, y_m)\) is given by:\[ x_m = \frac{x_1 + x_2}{2}, \quad y_m = \frac{y_1 + y_2}{2} \]Substituting the given points into the formula, we get:\[ x_m = \frac{-2 + (-22)}{2} = \frac{-24}{2} = -12 \]\[ y_m = \frac{6 + (-4)}{2} = \frac{2}{2} = 1 \]Thus, the midpoint is \((-12, 1)\).
02
Determine the Slope of the Original Line
The slope \(m\) of the line segment connecting the points \((-2,6)\) and \((-22,-4)\) is found using the slope formula:\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]Substituting the known values, we have:\[ m = \frac{-4 - 6}{-22 - (-2)} = \frac{-10}{-20} = \frac{1}{2} \]
03
Find the Slope of the Perpendicular Bisector
The slope of the perpendicular bisector is the negative reciprocal of the original line's slope. Since the original slope is \(\frac{1}{2}\), the perpendicular bisector's slope \(m_p\) is:\[ m_p = -\frac{1}{\frac{1}{2}} = -2 \]
04
Write the Equation of the Perpendicular Bisector
Now that we have the slope \(-2\) and the midpoint \((-12, 1)\), we can use the point-slope form of a line equation, which is:\[ y - y_1 = m(x - x_1) \]Substituting the midpoint and perpendicular slope into the equation:\[ y - 1 = -2(x + 12) \]Simplify to the slope-intercept form \(y = mx + b\):\[ y - 1 = -2x - 24 \]\[ y = -2x - 24 + 1 \]\[ y = -2x - 23 \]
05
Recheck the Calculations
Verify each calculation step to ensure accuracy:- Midpoint was determined correctly as \((-12,1)\).- Original slope \(\frac{1}{2}\) is correct.- Perpendicular slope \(-2\) is accurate as the negative reciprocal.- The equation \(y = -2x - 23\) fits the point \((-12,1)\) and has the proper slope.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Midpoint Calculation
Finding the midpoint of a line segment is like finding the middle point that splits the segment into two equal halves. If you have two endpoints, say (-2, 6) and (-22, -4), you apply the midpoint formula to find this central location.
The formula for the midpoint \((x_m, y_m)\) is:\[ x_m = \frac{x_1 + x_2}{2}, \quad y_m = \frac{y_1 + y_2}{2}\]
Let's break it down with our points:
The formula for the midpoint \((x_m, y_m)\) is:\[ x_m = \frac{x_1 + x_2}{2}, \quad y_m = \frac{y_1 + y_2}{2}\]
Let's break it down with our points:
- For the x-coordinate: \(-2\) and \(-22\) are averaged to find \(x_m\). So, \(x_m = \frac{-2 + (-22)}{2} = -12\).
- For the y-coordinate: The points 6 and -4 are averaged to find \(y_m\). Thus, \(y_m = \frac{6 + (-4)}{2} = 1\).
Slope Determination
To understand how steep or flat our original line segment is, we calculate its slope, which tells us the rate of change in y with respect to x.
The general formula for slope \(m\) is:\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]Using our given endpoints (-2,6) and (-22,-4), plug in the values:
Hence, the slope of the line segment is \(\frac{1}{2}\). A positive slope indicates the line rises as it moves from left to right.
The general formula for slope \(m\) is:\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]Using our given endpoints (-2,6) and (-22,-4), plug in the values:
- The change in y is \(-4 - 6 = -10\).
- The change in x is \(-22 - (-2) = -20\).
Hence, the slope of the line segment is \(\frac{1}{2}\). A positive slope indicates the line rises as it moves from left to right.
Point-Slope Form
The point-slope form is a way of expressing the equation of a line using a known point and the slope. It's especially useful when exploring perpendicular bisectors.
The formula looks like this:\[ y - y_1 = m(x - x_1) \]
For our perpendicular bisector, we use:
Simplifying to find the y-intercept form gives:
The formula looks like this:\[ y - y_1 = m(x - x_1) \]
For our perpendicular bisector, we use:
- The slope we've calculated, \(-2\),
- Our midpoint \((-12, 1)\) as the point \((x_1, y_1)\).
Simplifying to find the y-intercept form gives:
- Multiply: \(y - 1 = -2x - 24\).
- Add 1: \(y = -2x - 23\).
Negative Reciprocal of Slope
A perpendicular bisector has a special relationship with the line segment it intersects. Its slope is the negative reciprocal of the original line's slope, flipping and changing its sign.
To find a negative reciprocal:
To find a negative reciprocal:
- Take the given slope of the original line, \(\frac{1}{2}\).
- Flip it: The reciprocal is \(\frac{2}{1}\).
- Change the sign: The negative reciprocal becomes -2.