document.write( "Question 119097: Determine the value of 'k' if the product of the roots of 3kx^2+2(x-1)+k=0 is 1. \n" ); document.write( "
Algebra.Com's Answer #87259 by solver91311(24713)\"\" \"About 
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\"3kx%5E2%2B2%28x-1%29%2Bk=0\"\r
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\n" ); document.write( "\n" ); document.write( "Step 1: Put the equation into standard form, i.e. \"ax%5E2%2Bbx%2Bc=0\"\r
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\n" ); document.write( "\n" ); document.write( "\"3kx%5E2%2B2x-2%2Bk=0\" or more neatly: \"3kx%5E2%2B2x%2Bk-2=0\"\r
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\n" ); document.write( "\n" ); document.write( "Step 2: Apply the quadratic formula with \"a=3k\", \"b=2\", and \"c=k-2\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B-+sqrt%28+4-4%2A%283k%29%2A%28k-2%29+%29%29%2F%282%2A3k%29+\" \r
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\n" ); document.write( "\n" ); document.write( "Step 3: Simplify\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B-+sqrt%28+4-12k%5E2%2B24k%29+%29%2F%286k%29+\"\r
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\n" ); document.write( "\n" ); document.write( "Step 4: We are looking for k such that \"x%5B1%5Dx%5B2%5D=1\", so:\r
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\n" ); document.write( "\n" ); document.write( "Step 5: This looks like a hideous mess to multiply, but remember that \"%28a%2Bb%29%28a-b%29=a%5E2-b%5E2\", so:\r
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\n" ); document.write( "\n" ); document.write( "\"%284-%284-12k%5E2%2B24k%29%29%2F36k%5E2=1\"\r
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\n" ); document.write( "\n" ); document.write( "Step 6: Simplify and solve\r
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\n" ); document.write( "\n" ); document.write( "\"%284-%284-12k%5E2%2B24k%29%29%2F36k%5E2=1\"
\n" ); document.write( "\"%2812k%5E2-24k%29%2F36k%5E2=1\"
\n" ); document.write( "\"12k%5E2-24k=36k%5E2\"
\n" ); document.write( "\"-24k%5E2-24k=0\"
\n" ); document.write( "\"k%5E2%2Bk=0\"
\n" ); document.write( "\"k%28k%2B1%29=0\"\r
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\n" ); document.write( "\n" ); document.write( "So \"k+=+0\" or \"k=-1\"\r
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\n" ); document.write( "\n" ); document.write( "Step 7: \"k=0\" can be excluded because that would make the lead coefficient on the original quadradic go to zero. Therefore, \"k=-1\"\r
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\n" ); document.write( "\n" ); document.write( "Step 8: Check the answer. Using \"k=-1\", the original quadratic becomes\r
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\n" ); document.write( "\n" ); document.write( "\"-3x%5E2%2B2x-3=0\"\r
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\n" ); document.write( "\n" ); document.write( "The product of these two roots should be 1: Does \"%28%28-1%2Bsqrt%282%292i%29%2F3%29%28%28-1-sqrt%282%292i%29%2F3%29=1\"?\r
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\n" ); document.write( "\n" ); document.write( "Again, we can simplify something that looks rather messy with the difference of two squares factorization, \"%28a%2Bb%29%28a-b%29=a%5E2-b%5E2\", \r
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\n" ); document.write( "\n" ); document.write( ": Answer checks.
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