A line segment is bisected by a line with the equation - 6 y + 2 x = 3 . If one end of the line segment is at ( 4 , 8 ), where is the other end?

1 Answer
Jun 21, 2016

Any point on the line 3y-x=-27

Explanation:

Consider a horizontal line segment from (4,8) bisected by -6y+2x=3
The equation of the horizontal line segment from (4,8) is
color(white)("XXX")y=8

Noting that -6y+2x=3 rArr x=(6y+3)/2

The intersection of this horizontal line segment with the given bisector line will occur at
color(white)("XXX")((6(8)+3)/2,8)=(51/2,8)

Continuing to travel horizontally a point twice as far away from (4,8) as (51/2,8)
will be at (51,8)

That is (51,8) is one possible endpoint for a line segment form (4,8) bisected by -6y+2x=3 would be (51,8)

For any point which could be such an endpoint, a line through this point parallel to the bisecting line will provide all possible bisected line segment endpoints.

-6y+2x=3 (and all lines parallel to it) has a slope of 1/3

Using the previously determined possible endpoint (51,8) and this slope of 1/3
we can write the slope-point version:
color(white)("XXX")y-8=1/3(x-51)

color(white)("XXX")3y-24=x-51

color(white)("XXX")3y-x=-27

Any solution to the equation 3y-x=-27 will provide a valid endpoint for a line segment from (4,8) which will be bisected by 6y-2x=3

Here is a graph of the point and the two lines in question:
graph{(-6y+2x-3)(3y-x+27)((x-4)^2+(y-8)^2-0.02)=0 [-25.65, 25.64, -12.83, 12.81]}