document.write( "Question 149286: Determine whether the lines l1 and l2 are parallel, perpendicular, or neither.
\n" ); document.write( "Line l1 goes through (3, –8) and (–3, 9). Line l2 goes through (–1, –5) and (–7, 12). \n" ); document.write( "

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Determine whether the lines l1 and l2 are parallel, perpendicular, or neither.
\n" ); document.write( "Line l1 goes through (3, –8) and (–3, 9). Line l2 goes through (–1, –5) and (–7, 12).
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\n" ); document.write( "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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\n" ); document.write( "Line 1 thru (-3,9) and (3,-8). Always work \"left to right\", increasing x.
\n" ); document.write( "m1 = (y2-y1)/(x2-x1)
\n" ); document.write( "m1 = (-8-9)/(3 - (-3))
\n" ); document.write( "m1 = -17/6
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\n" ); document.write( "Line 2 thru (-7,12) and (-1,-5)
\n" ); document.write( "m2 = (-5 -12)/(-1 -(-7))
\n" ); document.write( "m2 = -17/6
\n" ); document.write( "m2 = m1, so they're parallel
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\n" ); document.write( "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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