document.write( "Question 168684: Which numbers cannot be used in place of the variable in each rational expression?\r
\n" ); document.write( "\n" ); document.write( "18. 2y + 1
\n" ); document.write( " y2 – y -6
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Algebra.Com's Answer #124369 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( "\"%282y%2B1%29%2F%28y%5E2-y-6%29\" Start with the given expression\r
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\n" ); document.write( "\n" ); document.write( "\"y%5E2-y-6=0\" Set the denominator equal to zero. Remember, dividing by 0 is undefined. So if we find values of y that make the denominator zero, then they cannot be used in place of the variable\r
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\n" ); document.write( "\n" ); document.write( "\"%28y-3%29%28y%2B2%29=0\" Factor the left side (note: if you need help with factoring, check out this solver)\r
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\n" ); document.write( "\n" ); document.write( "Now set each factor equal to zero:\r
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\n" ); document.write( "\n" ); document.write( "\"y-3=0\" or \"y%2B2=0\"\r
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\n" ); document.write( "\n" ); document.write( "\"y=3\" or \"y=-2\" Now solve for y in each case\r
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\n" ); document.write( "\n" ); document.write( "So our solutions are \"y=3\" or \"y=-2\"\r
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\n" ); document.write( "\n" ); document.write( "Since \"y=-2\" and \"y=3\" make the denominator equal to zero, this means these values CANNOT be used in the rational expression\r
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\n" ); document.write( "\n" ); document.write( "So \"y=-2\" and \"y=3\" cannot be used.
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