How can u tell whether these lines are parallel or perpendicular or neither with out graphing?
line 1; through (-1,9) and (-6,-6)
line 2; through (-7,-23) and (0,-2)

Question

How can u tell whether these lines are parallel or perpendicular or neither with out graphing?
 line 1; through (-1,9) and (-6,-6)
 line 2; through (-7,-23) and (0,-2)

anonymous · Answer

(-1,9) and (-6,-6) : slope =3
(-7,-23) and (0,-2): slope=3

same slope means lines are parallel

anonymous · Answer

how did you figure that out with out graphing?

hartnn · Answer

there is a formula to find the slope of line with 2 points given....

radar · Answer

They calculated the slope of each line using $$\Delta y \over \Delta x$$
When the slopes are equal to each other (in this case they were both 3) they are parallel.
If they were negative reciprocals like one was 3 and the other -1/3.  then they would of been perpendicular.

hartnn · Answer

for perpendicular,slopes must be negative inverse

anonymous · Answer

@radar I used that method....sorry for nothing showing my work.

anonymous · Answer

ohhhh. okay i got it. 
 and its okay @RyanL.

radar · Answer

@RyanL, good work, I was just trying to assist.  I want to explain what a negative reciprocal is, because by the questions being submitted he is going to need to understand that too.

anonymous · Answer

**She

radar · Answer

One number is a negative reciprocal of another number if their product is -1.

radar · Answer

Sorry "she".

anonymous · Answer

its alright.. and okay thanks.. again. lol