document.write( "Question 1189115: Two lines L1 :2y-3x-6=0and L2 :3y+x-20=0 intersect at point A. A third line L3 is perpendicular to L2 at point A. Find the equation of L3 \n" ); document.write( "
Algebra.Com's Answer #820371 by MathLover1(20850)\"\" \"About 
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Two lines
\n" ); document.write( "L1 : \"2y-3x-6=0\"
\n" ); document.write( "L2 : \"3y%2Bx-20=0+\"\r
\n" ); document.write( "\n" ); document.write( "intersect at point A\r
\n" ); document.write( "\n" ); document.write( "find the coordinates of the intersection point
\n" ); document.write( "\"2y-3x-6=0\".......solve for \"y\"
\n" ); document.write( "\"2y=3x%2B6\"
\n" ); document.write( "\"y=%283%2F2%29x%2B3\".........eq.1\r
\n" ); document.write( "\n" ); document.write( "\"3y%2Bx-20=0+\"
\n" ); document.write( "\"3y=-x%2B20+\"
\n" ); document.write( "\"y=-%281%2F3%29x%2B20%2F3+\"........eq.2\r
\n" ); document.write( "\n" ); document.write( "from eq.1 and eq.2 we have\r
\n" ); document.write( "\n" ); document.write( "\"+%283%2F2%29x%2B3=-%281%2F3%29x%2B20%2F3+\"......solve for \"x\"\r
\n" ); document.write( "\n" ); document.write( "\"+%283%2F2%29x%2B%281%2F3%29x=20%2F3+-3\"\r
\n" ); document.write( "\n" ); document.write( "\"+%2811x%29%2F6=11%2F3\"\r
\n" ); document.write( "\n" ); document.write( "\"+11x=6%2811%2F3%29\"\r
\n" ); document.write( "\n" ); document.write( "\"+11x=2%2811%29\"\r
\n" ); document.write( "\n" ); document.write( "\"+x=2%2811%29%2F11\"\r
\n" ); document.write( "\n" ); document.write( "\"+x=2\"\r
\n" ); document.write( "\n" ); document.write( "go to
\n" ); document.write( "\"y=%283%2F2%29x%2B3\".........eq.1, substitute \"x\"
\n" ); document.write( "\"y=%283%2F2%292%2B3\"
\n" ); document.write( "\"y=3%2B3\"
\n" ); document.write( "\"y=6\" \r
\n" ); document.write( "\n" ); document.write( "=> point A=(\"2\",\"6\")\r
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\n" ); document.write( "\n" ); document.write( "A third line L3 is perpendicular to L2 at point A.
\n" ); document.write( "perpendicular lines have slopes negative reciprocal to each other\r
\n" ); document.write( "\n" ); document.write( " line L2 in slope intercept form is \"y=-%281%2F3%29x%2B20%2F3+\"; so, slope is \"-1%2F3\"\r
\n" ); document.write( "\n" ); document.write( "negative reciprocal is \"-1%2F%28-1%2F3%29=3\"\r
\n" ); document.write( "\n" ); document.write( "=> a slope of the line L3 is \"3\"\r
\n" ); document.write( "\n" ); document.write( "to find the equation of L3, use a slope point formula\r
\n" ); document.write( "\n" ); document.write( "\"y-y%5B1%5D=m%28x-x%5B1%5D%29\" .....plug in a slope and coordinates of the point A\r
\n" ); document.write( "\n" ); document.write( "\"y-6=3%28x-2%29\"
\n" ); document.write( "\"y-6=3x-6\"
\n" ); document.write( "\"y=3x-6%2B6\"
\n" ); document.write( "\"y=3x+\"->answer\r
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