Parallel or Coincident lines

Question

Which of the following pair of equations form parallel lines? and which form coincident lines? Please explain how you can tell which is which.

1. 2x + 2Y = 90 Parallel or Coincident? Why?

   y= 10 - x

2. y + x = 25  Parallel or Coincident? Why?

   2x = 50 - 2y

 

Answer 1

1. Parallel because both lines have the same slope of -1 but different y-intercepts (45 and 10).

2. Coincident because the second equation can be converted to y + x  = 25, which is the same as the first equation.