document.write( "Question 1135670: When a polynomial f(x) is divided by x-3 the remainder is -9 and when divided by 2x-1 the remainder is -6.Find the remainder when f(x) is divided by(x-3)(2x-1) \n" ); document.write( "
Algebra.Com's Answer #753340 by MathLover1(20849)\"\" \"About 
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\n" ); document.write( "\n" ); document.write( "When a polynomial \"f%28x%29\" is divided by \"x-3\" the remainder is \"-9+\"\r
\n" ); document.write( "\n" ); document.write( "\"x-3=0\"=>\"x=3\"\r
\n" ); document.write( "\n" ); document.write( "=>\"f%283%29=-9\"\r
\n" ); document.write( "\n" ); document.write( "and when divided by \"2x-1\" the remainder is \"-6\"\r
\n" ); document.write( "\n" ); document.write( "\"%282x-1%29=0\"=>\"x=1%2F2\"\r
\n" ); document.write( "\n" ); document.write( "=>\"f%281%2F2%29=-6\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "We want the remainder when \"f%28x%29\" is divided by \"%28x-3%29%282x-1%29\". \r
\n" ); document.write( "\n" ); document.write( "So let \"f%28x%29+=+q%28x%29%28x-3%29%282x-1%29+%2B+r%28x%29\", where \"q\" is the quotient and \"r\" is the remainder. \r
\n" ); document.write( "\n" ); document.write( "Being the remainder on division by a quadratic, \"r\" must be a linear polynomial, say
\n" ); document.write( "\"r+=+ax%2Bb\".\r
\n" ); document.write( "\n" ); document.write( "So \"f%28x%29+=+q%28x%29%28x-3%29%282x%2B1%29+%2B+ax+%2B+b\"\r
\n" ); document.write( "\n" ); document.write( "\"f%283%29+=+-9\" means \"3a%2Bb+=+-+9\".....eq.1
\n" ); document.write( "\"f%281%2F2%29+=+-6+\"means \"%281%2F2%29a+%2B+b+=+-6\", or \"a+%2B+2b+=+-12\".....eq.2\r
\n" ); document.write( "\n" ); document.write( "Solve the system
\n" ); document.write( "\"3a%2Bb+=+-+9\".....eq.1
\n" ); document.write( "\"a+%2B+2b+=+-12\".....eq.2
\n" ); document.write( "----------------------------
\n" ); document.write( "\"3a%2Bb+=+-+9\".....eq.1.....solve for \"b\"\r
\n" ); document.write( "\n" ); document.write( "\"b+=+-+9-3a\"......substitute that into eq.2\r
\n" ); document.write( "\n" ); document.write( "\"a+%2B+2%28-+9-3a%29+=+-12\".....eq.2\r
\n" ); document.write( "\n" ); document.write( "\"a+%2B+-+18-6a+=+-12\"\r
\n" ); document.write( "\n" ); document.write( " \"-+18-5a+=+-12\"\r
\n" ); document.write( "\n" ); document.write( " \"-+18%2B12=+5a\"
\n" ); document.write( "
\n" ); document.write( "\"-+6=+5a+\"\r
\n" ); document.write( "\n" ); document.write( "\"a=-6%2F5\"\r
\n" ); document.write( "\n" ); document.write( "\"b+=+-+9-3a\"......substitute \"a\"
\n" ); document.write( "\"b+=-+9-3%28-6%2F5%29\"\r
\n" ); document.write( "\n" ); document.write( "\"b+=-+9%2B18%2F5\"\r
\n" ); document.write( "\n" ); document.write( "\"b+=-+45%2F5%2B18%2F5\"\r
\n" ); document.write( "\n" ); document.write( "\"b+=-+27%2F5\"\r
\n" ); document.write( "\n" ); document.write( "Conclusion: the remainder is \r
\n" ); document.write( "\n" ); document.write( "\"r+=+ax%2Bb\"....substitute \"a\" and \"b\"\r
\n" ); document.write( "\n" ); document.write( "\"r+=+-%286%2F5%29x-+27%2F5\"\r
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