document.write( "Question 149768: Graph the polynomial function \"P%28x%29=x%5E4%2Bx%5E3-3x%5E2-5x-2\" to approximately find the function's zeros, then use synthetic division and the remainder theorem to exactly find its zeros. \n" ); document.write( "
Algebra.Com's Answer #109867 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
First, let's graph the function \"P%28x%29=x%5E4%2Bx%5E3-3x%5E2-5x-2\" to get\r
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\n" ); document.write( "\n" ); document.write( "From the graph, we can see that the graph has the approximate zeros \"x=-1\" and \"x=2\"\r
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\n" ); document.write( "\n" ); document.write( "Now let's use the Rational Root Theorem to list all of the possible rational roots\r
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\n" ); document.write( "\n" ); document.write( "Rational Root Theorem:\r
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\n" ); document.write( "\n" ); document.write( " where p and q are the factors of the last and first coefficients\r
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\n" ); document.write( "\n" ); document.write( "So let's list the factors of -2 (the last coefficient):\r
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\n" ); document.write( "\n" ); document.write( "Now let's list the factors of 1 (the first coefficient):\r
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\n" ); document.write( "\n" ); document.write( "Now let's divide each factor of the last coefficient by each factor of the first coefficient\r
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\n" ); document.write( "\n" ); document.write( "Now simplify\r
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\n" ); document.write( "\n" ); document.write( "These are all the distinct rational zeros of the function that could occur\r
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\n" ); document.write( "\n" ); document.write( "Now let's use synthetic division to test each possible zero\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"1\" is really a root for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\" given the possible zero \"1\":\r
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1|11-3-5-2
| 12-1-6
12-1-6-8
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\n" ); document.write( "\n" ); document.write( "Since the remainder \"-8\" (the right most entry in the last row) is not equal to zero, this means that \"1\" is not a zero of \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"2\" is really a root for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\" given the possible zero \"2\":\r
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2|11-3-5-2
| 2662
13310
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\n" ); document.write( "\n" ); document.write( "Since the remainder \"0\" (the right most entry in the last row) is equal to zero, this means that \"2\" is a zero of \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"-1\" is really a root for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\" given the possible zero \"-1\":\r
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-1|11-3-5-2
| -1032
10-3-20
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\n" ); document.write( "\n" ); document.write( "Since the remainder \"0\" (the right most entry in the last row) is equal to zero, this means that \"-1\" is a zero of \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"-2\" is really a root for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"x%5E4%2Bx%5E3-3x%5E2-5x-2\" given the possible zero \"-2\":\r
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-2|11-3-5-2
| -2226
1-1-1-34
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\n" ); document.write( "\n" ); document.write( "Since the remainder \"4\" (the right most entry in the last row) is not equal to zero, this means that \"-2\" is not a zero of \"x%5E4%2Bx%5E3-3x%5E2-5x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So only \"-1\" and \"2\" are actually rational roots.\r
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\n" ); document.write( "\n" ); document.write( "Now looking back at the table for the test zero \"-1\", we see\r
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-1|11-3-5-2
| -1032
10-3-20
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\n" ); document.write( "\n" ); document.write( "The bottom row of coefficients (minus the last one) form the quotient\r
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\n" ); document.write( "\n" ); document.write( "Now let's perform synthetic division using the other zero \"2\" on the function \"x%5E3-3x-2\"\r
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2|10-3-2
| 242
1210
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\n" ); document.write( "\n" ); document.write( "Since the remainder \"0\" (the right most entry in the last row) is equal to zero, this means that \"2\" is a zero of \"x%5E3-3x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Once again the first three coefficients in the bottom row form the quotient \r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2%2B2x%2B1\"\r
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\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to find the zeros of \"x%5E2%2B2x%2B1\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4ac+%29%29%2F%282a%29\" Start with the quadratic formula\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-%282%29+%2B-+sqrt%28+%282%29%5E2-4%281%29%281%29+%29%29%2F%282%281%29%29\" Plug in \"a=1\", \"b=2\", and \"c=1\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B-+sqrt%28+4-4%281%29%281%29+%29%29%2F%282%281%29%29\" Square \"2\" to get \"4\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B-+sqrt%28+4-4+%29%29%2F%282%281%29%29\" Multiply \"4%281%29%281%29\" to get \"4\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B-+sqrt%28+0+%29%29%2F%282%281%29%29\" Subtract \"4\" from \"4\" to get \"0\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B-+sqrt%28+0+%29%29%2F%282%29\" Multiply \"2\" and \"1\" to get \"2\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B-+0%29%2F%282%29\" Take the square root of \"0\" to get \"0\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2+%2B+0%29%2F%282%29\" or \"x+=+%28-2+-+0%29%2F%282%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-2%29%2F%282%29\" or \"x+=++%28-2%29%2F%282%29\" Combine like terms. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+-1\" or \"x+=+-1\" Simplify. \r
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\n" ); document.write( "\n" ); document.write( "So the zeros of \"x%5E2%2B2x%2B1\" are \"x+=+-1\" or \"x+=+-1\" or just \"x+=+-1\" with a multiplicity of 2\r
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\n" ); document.write( "\n" ); document.write( "Now there are 3 instances where we get a zero of \"x+=+-1\". So this tells us that the zero \"x+=+-1\" has a multiplicity of 3\r
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\n" ); document.write( "\n" ); document.write( "So the zeros of \"P%28x%29=x%5E4%2Bx%5E3-3x%5E2-5x-2\" are \"-1\" (with a multiplicity of 3) and \"x=2\"
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