(a) Slope is rise over run, or change in y over change in x.
1 -> 3 ( )
2 -> 3 ( )
3 -> -1/3 ( )
(b) If a line is parallel, the slopes will be the same. If they are perpendicular, the slopes will be are negative reciprocals of one another. If they are neither, then their slopes don't match up in any way.
1 & 2 -> Parallel
1 & 3 -> Perpendicular
2 & 3 -> Perpendicular
Note - Since 1 & 2 are parallel, then both 1 and 2 will be perpendicular to 3!
Have a nice day!
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- Heather