Finding Values for m and b to Create a Symmetric Line

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  • Thread starter mathdad
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In summary, when it comes to finding the values for m and b so that the points (8, 2) and (4, 8) are symmetric about the line y = mx + b, you don't have to plug the coordinates of each point into the formula y = mx + b individually. You can use the slope of a line perpendicular to the line segment between (8, 2) and (4, 8) to find the values for m and b.
  • #1
mathdad
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Determine values for m and b so that the points (8, 2) and (4, 8) are symmetric about the line y = mx + b.

Do I plug the coordinates of each point into the formula
y = mx + b individually to find values for m and b?
 
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  • #2
RTCNTC said:
Determine values for m and b so that the points (8, 2) and (4, 8) are symmetric about the line y = mx + b.

Do I plug the coordinates of each point into the formula
y = mx + b individually to find values for m and b?
Before you get to that, what does it mean for the points to be symmetric about y = mx + b?

-Dan
 
  • #3
RTCNTC said:
Determine values for m and b so that the points (8, 2) and (4, 8) are symmetric about the line y = mx + b.

Do I plug the coordinates of each point into the formula
y = mx + b individually to find values for m and b?
Absolutely NOT! That would give you the equation of the line that contains (8, 2) and (4, 6) but these two points do NOT lie on the line you seek! They are symmetric about that line. In particular, the line you seek must be the perpendicular bisector of the line segment between (8, 2) and (4, 8).

What are the coordinates of the point midway between (8, 2) and (4, 6)? What is the slope of the line through (8, 2) and (4, 6)? What is the slope of a line perpendicular to that line? Finally, what is the equation of the line through that midpoint perpendicular to that line?
 
  • #4
HallsofIvy said:
Absolutely NOT! That would give you the equation of the line that contains (8, 2) and (4, 6) but these two points do NOT lie on the line you seek! They are symmetric about that line. In particular, the line you seek must be the perpendicular bisector of the line segment between (8, 2) and (4, 8).

What are the coordinates of the point midway between (8, 2) and (4, 6)? What is the slope of the line through (8, 2) and (4, 6)? What is the slope of a line perpendicular to that line? Finally, what is the equation of the line through that midpoint perpendicular to that line?

Thank you. I have been away from this site for more than 2 weeks.
 

Related to Finding Values for m and b to Create a Symmetric Line

1. What do m and b represent in the equation y = mx + b?

The variables m and b represent the slope and y-intercept, respectively, in a linear equation. The slope (m) is the measure of how steep the line is, while the y-intercept (b) is the point where the line intersects the y-axis.

2. How do I find the values for m and b in a given equation?

To find the values for m and b, you can use two points on the line. First, calculate the slope by finding the change in y over the change in x between the two points. Then, plug in the values of one of the points and the calculated slope into the equation y = mx + b and solve for b. This will give you the value of b, and you can then plug it back into the equation to find the value of m.

3. Can m and b have negative values?

Yes, both m and b can have negative values. The slope (m) can be positive or negative depending on the direction of the line, and the y-intercept (b) can also be negative if the line crosses the y-axis below the origin.

4. How do m and b affect the graph of a linear equation?

The value of m determines the steepness of the line, with a larger absolute value of m resulting in a steeper line. The value of b determines the y-intercept, or where the line crosses the y-axis. Changing the values of m and b will result in a different line with a different slope and y-intercept.

5. Can the values of m and b change in a linear equation?

Yes, the values of m and b can change in a linear equation. If the equation is in slope-intercept form (y = mx + b), then m and b can be adjusted to create different lines with different slopes and y-intercepts. However, if the equation is in standard form (Ax + By = C), then m and b cannot be changed as they are determined by the coefficients A and B.

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