document.write( "Question 1121470: Find the value of $a$ so that the lines with the given equations are perpendicular. \begin{align*}
\n" ); document.write( "y &= 2x+13 \\
\n" ); document.write( "6y+ax &= 6.
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Algebra.Com's Answer #737402 by ikleyn(52788)\"\" \"About 
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document.write( "y = 2x + 13 has the slope of  2.\r\n" );
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document.write( "6y +ax = 6   is the same as  y = \"%28-ax%2B6%29%2F6\"  and has the slope of  \"-a%2F6\".\r\n" );
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document.write( "You want to have \"-1%2F2\" = \"-a%2F6\"  (perpendicularity condition),  which leads you to\r\n" );
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document.write( "\"1%2F2\" = \"a%2F6\";   hence,  a = \"%281%2F2%29%2A6\" = 3.\r\n" );
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document.write( "Answer.  a = 3.\r\n" );
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