A line segment is bisected by a line with the equation 3 y - 8 x = 2 . If one end of the line segment is at (1 ,3 ), where is the other end?

1 Answer
Jan 17, 2017

The other end is at the point: (57/73,225/73)

Explanation:

When given a the equation of a line in standard form:

ax + by = c" [1]"

All lines perpendicular to the given line will be of the form:

-bx + ay = k" [2]"

where k is an arbitrary constant.

Write the given equation for the bisecting line in standard form:

8x - 3y = -2" [3]"

Write the equation for all lines perpendicular to equation [3]:

3x + 8y = k" [4]"

The start of the bisected line segment, (x_"start", y_"start"), is given as the point (1, 3)

Substitute 1 for x and 3 for y into equation [4] and solve for k:

3(1) + 8(3) = k

k = 27

The equation of the bisected line segment is:

3x + 8y = 27" [5]"

Add 8 times equation [3] to 3 times equation [5]:

64x - 24y + 9x + 24y = -16 + 81

73x = 65

x_"intersect" = 65/73

The x coordinate of the end can be found by adding the start coordinate to twice the change for the point of intersection:

x_"end" = x_"start" + 2(x_"intersect" - x_"start")

x_"end" = x_"start" + 2x_"intersect" - 2x_"start")

x_"end" = 2x_"intersect" - x_"start"

x_"end" = 2(65)/73 - 1

x_"end" = 57/73

Substitute 57/73 for x in equation [5] and the solve for the value of y_"end"

3(57/73) + 8y_"end" = 27

y_"end" = 27/8 - 3/8(57/73)

y_"end" = 225/73

Here is a graph of, the two lines, the start point, and the end point.

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