A line passes through #(3 ,2 )# and #(7 ,3 )#. A second line passes through #(8 , 1 )#. What is one other point that the second line may pass through if it is parallel to the first line?

1 Answer
Jan 23, 2017

Many possible answers, including #(12, 2)# and #(4, 0)#

Explanation:

Lines are parallel if they have the same slope.

So, to answer this question, we need to:
1. Find the slope of the first line
2. Apply that slope to the second line to find a corresponding point

SOLUTION

  1. Slope of first line
    Slope or #m# can be found by: #m=(Delta y)/(Delta x)=(y_2 - y_1)/(x_2 - x_1)#
    Using the given information, #m=(3 - 2)/(7 - 3)=color(blue)(1/4)#
    Both lines will have a slope of #1/4#
  2. Using #m=1/4#, find a point on the second line

Here, there are infinite possibilities for points on the second line.
If we use the point #(8,1)# as #(x_1, y_1)#, then #(x_2, y_2)# must
satisfy the equation

#m=1/4=(y_2 - y_1)/(x_2 - x_1)#

The easiest solutions can be found by using #Delta y=1# and #Delta x=4#

#Delta y = 1#
#y_2 - y_1 = 1#
#y_2 - 1 = 1#
#color(blue)(y_2 = 2)#

#Delta x = 4#
#x_2 - x_1 = 4#
#x_2 - 8 = 4#
#color(blue)(x_2 = 12)#

One solution is #(12, 2)#

Another solution can be found by solving
#1 - y = 1# and #8 - x = 4#

But as stated earlier, there are many, many more valid solutions.