document.write( "Question 148299: (22 pts) Consider the polynomial f(x) = 2x^3 – 3x^2 – 8x – 3.\r
\n" ); document.write( "\n" ); document.write( "(i) By using the Rational Zero Theorem, list all possible rational zeros of the given polynomial.\r
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\n" ); document.write( "\n" ); document.write( "(ii) Find all of the zeros of the given polynomial. Be sure to show work, explaining how you have found them.\r
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Algebra.Com's Answer #108699 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
i)\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 -3 (the last coefficient):\r
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\n" ); document.write( "\n" ); document.write( "Now let's list the factors of 2 (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( "ii)\r
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\n" ); document.write( "\n" ); document.write( "With the help of a graphing calculator, we see that -1 is a zero of \"2x%5E3-3x%5E2-8x-3\"\r
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\n" ); document.write( "\n" ); document.write( "note: let me know if you need to find the zeros a different way.\r
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\n" ); document.write( "\n" ); document.write( "So let's set up a synthetic division table by placing the value -1 in the upper left corner and placing the coefficients of the polynomial to the right of -1.\n" ); document.write( "\n" ); document.write( "
-1|2-3-8-3
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\n" ); document.write( "\n" ); document.write( "Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 2)\r
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-1|2-3-8-3
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2
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\n" ); document.write( "\n" ); document.write( " Multiply -1 by 2 and place the product (which is -2) right underneath the second coefficient (which is -3)\r
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-1|2-3-8-3
|-2
2
\r
\n" ); document.write( "\n" ); document.write( " Add -2 and -3 to get -5. Place the sum right underneath -2.\r
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-1|2-3-8-3
|-2
2-5
\r
\n" ); document.write( "\n" ); document.write( " Multiply -1 by -5 and place the product (which is 5) right underneath the third coefficient (which is -8)\r
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-1|2-3-8-3
|-25
2-5
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\n" ); document.write( "\n" ); document.write( " Add 5 and -8 to get -3. Place the sum right underneath 5.\r
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-1|2-3-8-3
|-25
2-5-3
\r
\n" ); document.write( "\n" ); document.write( " Multiply -1 by -3 and place the product (which is 3) right underneath the fourth coefficient (which is -3)\r
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-1|2-3-8-3
|-253
2-5-3
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\n" ); document.write( "\n" ); document.write( " Add 3 and -3 to get 0. Place the sum right underneath 3.\r
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-1|2-3-8-3
|-253
2-5-30
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\n" ); document.write( "\n" ); document.write( "Since the last column adds to zero, this means that -1 is a zero of \"2x%5E3-3x%5E2-8x-3\" (this confirms our original claim). \r
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\n" ); document.write( "\n" ); document.write( "Now lets look at the bottom row of coefficients:\r
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\n" ); document.write( "\n" ); document.write( "The first 3 coefficients (2,-5,-3) form the quotient\r
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\n" ); document.write( "\n" ); document.write( "\"2x%5E2+-+5x+-+3\"\r
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\n" ); document.write( "\n" ); document.write( "So \"%282x%5E3+-+3x%5E2+-+8x+-+3%29%2F%28x%2B1%29=2x%5E2+-+5x+-+3\"\r
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\n" ); document.write( "\n" ); document.write( "Basically \"2x%5E3+-+3x%5E2+-+8x+-+3\" factors to \"%28x%2B1%29%282x%5E2+-+5x+-+3%29\"\r
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\n" ); document.write( "\n" ); document.write( "Now lets find the zeros for \"2x%5E2+-+5x+-+3\".\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-%28-5%29+%2B-+sqrt%28+%28-5%29%5E2-4%282%29%28-3%29+%29%29%2F%282%282%29%29\" Plug in \"a=2\", \"b=-5\", and \"c=-3\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B-+sqrt%28+%28-5%29%5E2-4%282%29%28-3%29+%29%29%2F%282%282%29%29\" Negate \"-5\" to get \"5\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B-+sqrt%28+25-4%282%29%28-3%29+%29%29%2F%282%282%29%29\" Square \"-5\" to get \"25\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B-+sqrt%28+25--24+%29%29%2F%282%282%29%29\" Multiply \"4%282%29%28-3%29\" to get \"-24\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B-+sqrt%28+25%2B24+%29%29%2F%282%282%29%29\" Rewrite \"sqrt%2825--24%29\" as \"sqrt%2825%2B24%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B-+sqrt%28+49+%29%29%2F%282%282%29%29\" Add \"25\" to \"24\" to get \"49\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B-+sqrt%28+49+%29%29%2F%284%29\" Multiply \"2\" and \"2\" to get \"4\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B-+7%29%2F%284%29\" Take the square root of \"49\" to get \"7\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%285+%2B+7%29%2F%284%29\" or \"x+=+%285+-+7%29%2F%284%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%2812%29%2F%284%29\" or \"x+=++%28-2%29%2F%284%29\" Combine like terms. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+3\" or \"x+=+-1%2F2\" Simplify. \r
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\n" ); document.write( "\n" ); document.write( "So the zeros of \"2x%5E3-3x%5E2-8x-3\" are \"x=-1\", \"x=3\", or \"x=-1%2F2\"
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