A line segment is bisected by a line with the equation 4 y - 6 x = 8 . If one end of the line segment is at ( 7 , 3 ), where is the other end?

1 Answer
Mar 12, 2017

Any point on the line color(purple)(2y-3x=23)
or
if the given line color(red)(4y-6x=8) is to be a perpendicular bisector then color(brown)(""(-23/15,46/5))

Explanation:

Apology:
Even omitting some details, this explanation is quite long.

Consider the vertical line x=7 which passes through the given point (7,3)
This vertical line will intersect color(red)(4y-6x=8) at (7,25/2), a point which is 25/2-3=19/2 above the given point color(green)(""(7,3))
A point twice as far above color(green)(""(7,3)) would be at (7,3+2xx19/2)=(7,22)
That is the line segment from color(green)(""(7,3)) to (7,22) is bisected by color(red)("4y-6x=8)
enter image source here

Furthermore, as we can see from similar triangles any line parallel to color(red)(4y-6x=8) and through (7,22) gives an infinite collection of points, any one of which would serve as an endpoint with color(green)(""(7,3)) for a line segment bisected by color(red)(4y-6x=8)

enter image source here
color(red)(4y-6x=8) has a slope of 3/2
so any line parallel to it must also have a slope of 3/2
and
if such a line passes through (7,22) then we can write its equation using the slope-point form:
color(white)("XXX")y-22=3/2(x-7)
or simplified as
color(white)("XXX")color(purple)(2y-3x=23)

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It is possible, since this question was asked under the heading "Perpendicular Bisectors" that it was intended that color(red)(4y-6x=8) should be the perpendicular bisector of a derived line segment.

In this case the perpendicular line to color(red)(4y-6x=8) passing through color(green)(""(7,3))
would have a slope of -2/3 (the negative inverse of color(red)(4y-6x=8) and (again, working through the slope-point form)
an equation of color(brown)(3y+2x=23)
enter image source here
The system of equations:
color(purple)(2y-3x=23)
color(brown)(3y+2x=23)
can be solved for the point of intersection: color(brown)(""(-23/15,46/5))