SOLUTION: Determine whether the lines l1 and l2 are parallel, perpendicular, or neither. Line l1 goes through (3, �8) and (�3, 9). Line l2 goes through (�1, �5) and (�7, 12).

Question 149286: Determine whether the lines l1 and l2 are parallel, perpendicular, or neither.
Line l1 goes through (3, �8) and (�3, 9). Line l2 goes through (�1, �5) and (�7, 12).
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Determine whether the lines l1 and l2 are parallel, perpendicular, or neither.
Line l1 goes through (3, �8) and (�3, 9). Line l2 goes through (�1, �5) and (�7, 12).
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Find the slopes of the 2 lines. If the slopes are the same, they're parallel. If the slope of one (m) and the other is -1/m, they're perpendicular.
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Line 1 thru (-3,9) and (3,-8). Always work "left to right", increasing x.
m1 = (y2-y1)/(x2-x1)
m1 = (-8-9)/(3 - (-3))
m1 = -17/6
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Line 2 thru (-7,12) and (-1,-5)
m2 = (-5 -12)/(-1 -(-7))
m2 = -17/6
m2 = m1, so they're parallel
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Working with increasing values of x is a convention, meaning something that's agreed on. Without that, the values of m could be inverted depending on the order a person chose.

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