A line passes through (3,9) and (5,1). A second line passes through (7,6). What is one other point that the second line may pass through if it is parallel to the first line?

1 Answer
Sep 22, 2016

Any point other than (7,6) and satisfying the condition 4x+y=34 could be such a point. Examples are (0,34), (8,66) and (12,14).

Explanation:

A line passing through (x1,y1) and (x2,y2) has a slope of y2y1x2x1. Hence slope of line joining (3,9) and (5,1) is

1953=82=4

As the second line passing through (7,6) is parallel to the above, its slope too is 4.

Now, equation of a line passing through (x1,y1) and having a slope of m is (yy1)=m(xx1). Hence, the equation of line passing through (7,6) and having a slope of 4 is

(y6)=4(x7) or y6=4x+28 i.e. 4x+y=34

Hence, any point satisfying the condition 4x+y=34 (other than (7,6) will satisfy this.

Let x=0 then y=34, hence point could be (0,34) or

let x=8 then y=66, hence other point could be (8,66) or

let x=12 then y=14, hence point could be (12,14)