document.write( "Question 199775: Hi!\r
\n" ); document.write( "\n" ); document.write( "Find all real zeros of the polynomial. Use the quadratic formula if necessary.\r
\n" ); document.write( "\n" ); document.write( "P(x) = 4x^3 - 7x^2 - 10x - 2\r
\n" ); document.write( "\n" ); document.write( "thanks for the homework help!
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Algebra.Com's Answer #150137 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
First, let's find the possible rational zeros of P(x):\r
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\n" ); document.write( "\n" ); document.write( "Any rational zero can be found through this equation\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 4 (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 test the possible rational zeros to see which ones are actually roots.\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 \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"1\":\r
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1|4-7-10-2
| 4-3-13
4-3-13-15
\r
\n" ); document.write( "\n" ); document.write( "Since the remainder \"-15\" (the right most entry in the last row) is not equal to zero, this means that \"1\" is not a zero of \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"1%2F2\" is really a root for the function \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"1%2F2\":\r
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1/2|4-7-10-2
| 2-5/2-25/4
4-5-25/2-33/4
\r
\n" ); document.write( "\n" ); document.write( "Since the remainder \"-33%2F4\" (the right most entry in the last row) is not equal to zero, this means that \"1%2F2\" is not a zero of \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"1%2F4\" is really a root for the function \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"1%2F4\":\r
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1/4|4-7-10-2
| 1-3/2-23/8
4-6-23/2-39/8
\r
\n" ); document.write( "\n" ); document.write( "Since the remainder \"-39%2F8\" (the right most entry in the last row) is not equal to zero, this means that \"1%2F4\" is not a zero of \"4x%5E3-7x%5E2-10x-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 \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"2\":\r
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2|4-7-10-2
| 82-16
41-8-18
\r
\n" ); document.write( "\n" ); document.write( "Since the remainder \"-18\" (the right most entry in the last row) is not equal to zero, this means that \"2\" is not a zero of \"4x%5E3-7x%5E2-10x-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 \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"-1\":\r
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-1|4-7-10-2
| -411-1
4-111-3
\r
\n" ); document.write( "\n" ); document.write( "Since the remainder \"-3\" (the right most entry in the last row) is not equal to zero, this means that \"-1\" is not a zero of \"4x%5E3-7x%5E2-10x-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 \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"-1\":\r
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-1|4-7-10-2
| -411-1
4-111-3
\r
\n" ); document.write( "\n" ); document.write( "Since the remainder \"-3\" (the right most entry in the last row) is not equal to zero, this means that \"-1\" is not a zero of \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"-1%2F2\" is really a root for the function \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"-1%2F2\":\r
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-1/2|4-7-10-2
| -29/211/4
4-9-11/23/4
\r
\n" ); document.write( "\n" ); document.write( "Since the remainder \"3%2F4\" (the right most entry in the last row) is not equal to zero, this means that \"-1%2F2\" is not a zero of \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's see if the possible zero \"-1%2F4\" is really a root for the function \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So let's make the synthetic division table for the function \"4x%5E3-7x%5E2-10x-2\" given the possible zero \"-1%2F4\":\r
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-1/4|4-7-10-2
| -122
4-8-80
\r
\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%2F4\" is a zero of \"4x%5E3-7x%5E2-10x-2\"\r
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\n" ); document.write( "\n" ); document.write( "So this tells us that \"4x%5E3-7x%5E2-10x-2=%284x%2B1%29%28x%5E2-2x-2%29\"\r
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\n" ); document.write( "\n" ); document.write( "Note: the quotient results from taking a quarter of the first three values in the bottom row.\r
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\n" ); document.write( "\n" ); document.write( "Now let's solve \"x%5E2-2x-2=0\" to find the next two zeros.\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2-2x-2=0\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "Notice we have a quadratic in the form of \"Ax%5E2%2BBx%2BC\" where \"A=1\", \"B=-2\", and \"C=-2\"\r
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\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to solve for \"x\":\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-%28-2%29+%2B-+sqrt%28+%28-2%29%5E2-4%281%29%28-2%29+%29%29%2F%282%281%29%29\" Plug in \"A=1\", \"B=-2\", and \"C=-2\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%282+%2B-+sqrt%28+%28-2%29%5E2-4%281%29%28-2%29+%29%29%2F%282%281%29%29\" Negate \"-2\" to get \"2\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%282+%2B-+sqrt%28+4-4%281%29%28-2%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+=+%282+%2B-+sqrt%28+4--8+%29%29%2F%282%281%29%29\" Multiply \"4%281%29%28-2%29\" to get \"-8\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%282+%2B-+sqrt%28+4%2B8+%29%29%2F%282%281%29%29\" Rewrite \"sqrt%284--8%29\" as \"sqrt%284%2B8%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%282+%2B-+sqrt%28+12+%29%29%2F%282%281%29%29\" Add \"4\" to \"8\" to get \"12\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%282+%2B-+sqrt%28+12+%29%29%2F%282%29\" Multiply \"2\" and \"1\" to get \"2\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%282+%2B-+2%2Asqrt%283%29%29%2F%282%29\" Simplify the square root (note: If you need help with simplifying square roots, check out this solver) \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%282%29%2F%282%29+%2B-+%282%2Asqrt%283%29%29%2F%282%29\" Break up the fraction. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+1+%2B-+sqrt%283%29\" Reduce. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+1%2Bsqrt%283%29\" or \"x+=+1-sqrt%283%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "So the next two roots are \"x+=+1%2Bsqrt%283%29\" or \"x+=+1-sqrt%283%29\" \r
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\n" ); document.write( "\n" ); document.write( "Answer:\r
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\n" ); document.write( "\n" ); document.write( "So the three real zeros of \"P%28x%29+=+4x%5E3+-+7x%5E2+-+10x+-+2\" are:\r
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\n" ); document.write( "\n" ); document.write( "\"x=-1%2F4\", \"x+=+1%2Bsqrt%283%29\" or \"x+=+1-sqrt%283%29\" \r
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\n" ); document.write( "\n" ); document.write( "If you have any questions, email me at jim_thompson5910@hotmail.com
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