document.write( "Question 95786: Are line L, through (6,1) and (9,7) and L2 through (-9,8) and (10,9) parallel or do they intersect? \n" ); document.write( "
Algebra.Com's Answer #69795 by Edwin McCravy(20086)\"\" \"About 
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document.write( "Are line L, through (6,1) and (9,7) and L2 through (-9,8) and (10,9) parallel\r\n" );
document.write( "or do they intersect?\r\n" );
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document.write( "First let's draw those lines and see how they look:\r\n" );
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document.write( "They certainly look like they intersect and are not parallel.  But \"looking and\r\n" );
document.write( "seeing\", though it is a good check, it is not considered good mathematics.  So\r\n" );
document.write( "we calculate the slope of each line.\r\n" );
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document.write( "Unless their slopes are the same, they aren't parallel and will intersect.\r\n" );
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document.write( "Use the slope formula for the green line, where\r\n" );
document.write( "(x1,y1) = (6,1) and (x2,y2) = (9,7)\r\n" );
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document.write( "     y2 - y1     7 - 1     6\r\n" );
document.write( "m = --------- = ------- = --- = 2\r\n" );
document.write( "     x2 - x1     9 - 6     3\r\n" );
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document.write( "Use the slope formula for the blue line, where\r\n" );
document.write( "(x1,y1) = (-9,8) and (x2,y2) = (10,9)\r\n" );
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document.write( "     y2 - y1      9 - 8          1        1\r\n" );
document.write( "m = --------- = ---------- = -------- = ----\r\n" );
document.write( "     x2 - x1    10 - (-9)     10 + 9     19 \r\n" );
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document.write( "Well, 2 and 1/19 are certainly not equal so\r\n" );
document.write( "that proves they are not parallel and therefore\r\n" );
document.write( "they intersect.\r\n" );
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document.write( "Incidentally they intersect at the point (\"9\"\"18%2F37\", \"8\"\"36%2F37\")\r\n" );
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document.write( "Edwin
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