Chapter 1: Problem 67
Exer. \(67-68\) : Find an equation for the perpendicular bisector of \(A B\). \(A(3,-1), B(-2,6)\)
Short Answer
Expert verified
The equation of the perpendicular bisector is \(y = \frac{5}{7}x + \frac{15}{14}\).
Step by step solution
01
Find the Midpoint of AB
To find the midpoint of the line segment \(AB\), use the midpoint formula: \( M = \left( \frac{x_1 + x_2}{2}, \frac{y_1+y_2}{2} \right) \). Substituting \(A(3, -1)\) and \(B(-2, 6)\), we get the midpoint \( M = \left( \frac{3 + (-2)}{2}, \frac{-1 + 6}{2} \right) = \left( \frac{1}{2}, rac{5}{2} \right) \).
02
Determine the Slope of AB
The slope of a line between two points \((x_1, y_1)\) and \((x_2, y_2)\) is given by \( m = \frac{y_2 - y_1}{x_2 - x_1} \). Substituting the coordinates of \(A\) and \(B\), the slope \(m = \frac{6 - (-1)}{-2 - 3} = \frac{7}{-5} = -\frac{7}{5} \).
03
Calculate the Slope of the Perpendicular Bisector
The slope of the perpendicular bisector is the negative reciprocal of the slope of \(AB\). Thus, it is \(-\left( -\frac{5}{7} \right) = \frac{5}{7}\).
04
Form the Equation of the Perpendicular Bisector
Using the point-slope form of the line equation \(y - y_1 = m(x - x_1)\), where \(m\) is the slope and \((x_1, y_1)\) is the midpoint, substitute the calculated slope \(\frac{5}{7}\) and point \(\left( \frac{1}{2}, rac{5}{2} \right)\). The equation becomes \(y - \frac{5}{2} = \frac{5}{7}\left(x - \frac{1}{2}\right)\). Simplify to obtain the equation: \[ y = \frac{5}{7}x + \frac{15}{14}\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
midpoint formula
The midpoint formula is a vital tool in geometry, especially when dealing with line segments. It helps you find the exact middle point between two endpoints of a line segment. To apply the midpoint formula, you need the coordinates of both endpoints, say \( (x_1, y_1) \) and \( (x_2, y_2) \).
- First, add the \( x \) coordinates of the endpoints and divide the sum by 2. This calculation gives the \( x \) coordinate of the midpoint.
- Second, add the \( y \) coordinates and divide by 2 for the \( y \) coordinate of the midpoint.
- The \( x \) value is \( \frac{3 + (-2)}{2} = \frac{1}{2} \)
- The \( y \) value is \( \frac{-1 + 6}{2} = \frac{5}{2} \)
slope of a line
The slope of a line is a measure of its steepness and direction. It's calculated using the coordinates of two points on the line, let's call them \((x_1, y_1)\) and \((x_2, y_2)\). The formula for finding the slope (\( m \)) is:\[m = \frac{y_2 - y_1}{x_2 - x_1}\]Here's a simple way to understand it:
- The numerator \((y_2 - y_1)\) represents the change in vertical distance, or rise.
- The denominator \((x_2 - x_1)\) represents the horizontal change, or run.
- \(y\) difference: \(6 - (-1) = 7\)
- \(x\) difference: \(-2 - 3 = -5\)
- Thus, \( m = \frac{7}{-5} = -\frac{7}{5} \)
point-slope form
The point-slope form is a handy tool for writing the equation of a line when you know its slope and a point on the line. The standard form is:\[y - y_1 = m(x - x_1)\]Here’s how it works:
- \(m\) is the slope of the line.
- \((x_1, y_1)\) is a known point on the line.
- \(y - \frac{5}{2} = \frac{5}{7}(x - \frac{1}{2})\)
- Multiply: \(5(x - \frac{1}{2})\) to achieve: \(y - \frac{5}{2} = \frac{5}{7}x - \frac{5}{14}\)
negative reciprocal
Understanding the negative reciprocal is key when dealing with perpendicular lines. If you know the slope of a line, the slope of a line perpendicular to it is the negative reciprocal of the original slope.Here's how it works:
- Take the original slope, say \( m \).
- Find its reciprocal by flipping the fraction (if it's \( \frac{a}{b} \), the reciprocal is \( \frac{b}{a} \)).
- Make it negative, so if the reciprocal is positive, it will become negative, and vice versa.
- Reciprocal of \(-\frac{7}{5}\) is \(-\frac{5}{7}\)
- Convert to positive: \(\frac{5}{7}\)