document.write( "Question 323586: \"+log%28+2%2C+a+%29+%2B+log%28+a%2C+4%29=+3\"\r
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Algebra.Com's Answer #231528 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
Change of base formula: \"log%28b%2C%28x%29%29=ln%28x%29%2Fln%28b%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"log%282%2C%28a%29%29%2Blog%28a%2C%284%29%29=3\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"ln%28a%29%2Fln%282%29%2Bln%284%29%2Fln%28a%29=3\" Use the change of base formula (shown above)\r
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\n" ); document.write( "\n" ); document.write( "\"ln%28a%29%2Aln%28a%29%2Bln%284%29%2Aln%282%29=3%2Aln%282%29%2Aln%28a%29\" Multiply EVERY term by the LCD \"ln%282%29%2Aln%28a%29\" to clear out the fractions.\r
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\n" ); document.write( "\n" ); document.write( "Now let's make \"z=ln%28a%29\". This then means that we get\r
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\n" ); document.write( "\n" ); document.write( "\"z%2Az%2Bln%284%29%2Aln%282%29=3%2Aln%282%29%2Az\"\r
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\n" ); document.write( "\n" ); document.write( "\"z%5E2%2Bln%284%29%2Aln%282%29=3%2Aln%282%29%2Az\" Rewrite \"z%2Az\" to get \"z%5E2\"\r
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\n" ); document.write( "\n" ); document.write( "\"z%5E2-3%2Aln%282%29%2Az%2Bln%284%29%2Aln%282%29=0\" Subtract \"3%2Aln%282%29%2Az\" from both sides.\r
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\n" ); document.write( "\n" ); document.write( "It may be hard to see, but the equation is now in the form \"Az%5E2%2BBz%2BC=0\". To solve for 'z', use the quadratic formula \r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%28-B+%2B-+sqrt%28+B%5E2-4AC+%29%29%2F%282A%29+\"\r
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\n" ); document.write( "\n" ); document.write( "In this case, \"A=1\", \"B=-3%2Aln%282%29\" and \"C=ln%284%29%2Aln%282%29\". Plug all this into the formula to get\r
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\n" ); document.write( "\n" ); document.write( " Square \"-3%2Aln%282%29\" to get \"9%2A%28ln%282%29%29%5E2\" and multiply\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B-+sqrt%28ln%282%29%289%2Aln%282%29-4%2Aln%284%29%29+%29%29%2F2+\" Factor out the GCF \"ln%282%29\" from the terms under the radical.\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B-+sqrt%28ln%282%29%28ln%282%5E9%29-ln%284%5E4%29%29+%29%29%2F2+\" Use the identity \"y%2Aln%28x%29=ln%28x%5Ey%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B-+sqrt%28ln%282%29%28ln%28512%29-ln%28256%29%29+%29%29%2F2+\" Raise 2 to the 9th power to get 512 and raise 4 to the 4th power to get 256.\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B-+sqrt%28ln%282%29%28ln%28512%2F256%29%29+%29%29%2F2+\" Combine the logs using the identity \"ln%28A%29-ln%28B%29=ln%28A%2FB%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B-+sqrt%28ln%282%29%2Aln%282%29+%29%29%2F2+\" Divide\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B-+sqrt%28%28ln%282%29%29%5E2+%29%29%2F2+\" Rewrite \"ln%282%29%2Aln%282%29\" as \"%28ln%282%29%29%5E2\"\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B-+ln%282%29%29%2F2+\" Take the square root of \"%28ln%282%29%29%5E2\" to get \"ln%282%29\"\r
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\n" ); document.write( "\n" ); document.write( "The plus/minus then breaks down into two equations: \"z+=+%283%2Aln%282%29+%2B+ln%282%29%29%2F2+\" or \"z+=+%283%2Aln%282%29+-+ln%282%29%29%2F2+\"\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+%2B+ln%282%29%29%2F2+\" Start with the first equation.\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%284%2Aln%282%29%29%2F2+\" Add\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+2%2Aln%282%29+\" Reduce.\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+ln%282%5E2%29+\" Use the identity \"y%2Aln%28x%29=ln%28x%5Ey%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+ln%284%29+\" Square 2 to get 4.\r
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\n" ); document.write( "\n" ); document.write( "Since we let \"z=ln%28a%29\", this means that \"ln%284%29=ln%28a%29\" and that \"a=4\" is one solution.\r
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\n" ); document.write( "\n" ); document.write( "Now move onto the second equation\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%283%2Aln%282%29+-+ln%282%29%29%2F2+\" Start with the second equation.\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+%282%2Aln%282%29+%29%2F2+\" Subtract\r
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\n" ); document.write( "\n" ); document.write( "\"z+=+ln%282%29+\" Reduce.\r
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\n" ); document.write( "\n" ); document.write( "Again, we let \"z=ln%28a%29\", meaning that \"ln%28a%29=ln%282%29\" which implies that \"a=2\"\r
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\n" ); document.write( "\n" ); document.write( "So \"a=2\" is the other solution. We know that there are only two solutions here because we're dealing with a quadratic.\r
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\n" ); document.write( "\n" ); document.write( "So the two solutions are \"a=2\" or \"a=4\"\r
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