document.write( "Question 128875: line 1 passes through the points (1,-2) and (-2,-4)
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Algebra.Com's Answer #94254 by solver91311(24713)\"\" \"About 
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document.write( "Discussion
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document.write( "The equation of a line passing through two points is given by \"y-y%5B1%5D=%28%28y%5B1%5D-y%5B2%5D%29%2F%28x%5B1%5D-x%5B2%5D%29%29%28x-x%5B2%5D%29\".
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document.write( "You need to derive the equations for both of your
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document.write( "lines and then put them into slope-intercept form \"y=mx%2Bb\", so that you can
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document.write( "compare the slope numbers for the two lines.\r
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document.write( "Lines are parallel if and only if their slopes are equal, i.e. \"m%5B1%5D=m%5B2%5D\".\r
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document.write( "Lines are perpendicular if and only if their slopes are negative reciprocals,
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document.write( "i.e. \"m%5B1%5D=-1%2Fm%5B2%5D\" 
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document.write( "Solution
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document.write( "Line 1:
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document.write( "\"y-%28-2%29=%28%28%28-2%29-%28-4%29%29%2F%281-%28-2%29%29%29%28x-%28-2%29%29\"
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document.write( "\"y%2B2=%282%2F3%29%28x%2B2%29\"
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document.write( "\"y%2B2=2x%2F3%2B4%2F3\"
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document.write( "\"y=2x%2F3-2%2F3\"\r
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document.write( "Line 2:
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document.write( "\"y-2=%28%282-5%29%2F%282-0%29%29%28x-2%29\"
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document.write( "\"y-2=%28-3%2F2%29%28x-2%29\"
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document.write( "\"y-2=-3x%2F2%2B3\"
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document.write( "\"y=-3x%2F2%2B5\"\r
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document.write( "The slope of Line 1 is \"2%2F3\".  The negative reciprocal of \"2%2F3\" is \"-3%2F2\" which is the slope of Line 2.\r
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document.write( "Therefore the lines are perpendicular.\r
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document.write( "Check Answer
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document.write( "They look perpendicular to me:\r
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