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

1 Answer
Jul 15, 2016

The other end could be any point on the line y=2x-1

Explanation:

For convenience, I will rearrange the given equation
color(white)("XXX")-3y+6x=6
as
color(white)("XXX")y=2x-2

Consider the vertical line through (3,3).
Since x is constant for all points on a vertical line,
this vertical line will intersect y=2x-2 at (3,4)

The distance between (3,3) and (3,4) is 1 unit.

The point (3,5) is also on this vertical line at a distance of 2 units from (3,3).

Therefore y=2x-2 (originally given as -3y+6x=6) bisects the line segment joining (3,3) and (3,5).

Therefore one possible endpoint would be at (3,5)

enter image source here

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Perhaps less obviously, any point on a line through (3,5) and parallel to the given line y=2x-2 (or in its original but less convenient form -3y+6x=6)
will also be a line segment endpoint bisected by the given equation.
enter image source here
From the image above we can see that for an arbitrary point E on a line parallel to the given bisector line
triangle ABD ~ triangle ACE
and since abs(AB)=1/2abs(AC)
rarr abs(AD)=1/2abs(AE)
(i.e. the given line is a bisector for AE)

Since y=2x-2 has a slope of 2
the line parallel to it and through (3,5) will also have a slope of 2
and using the slope-point form:
color(white)("XXX")y-5=2(x-3)
Which can be simplified as
color(white)("XXX")y=2x-1