document.write( "Question 123010: I neeed help asap please.\r
\n" ); document.write( "\n" ); document.write( "Use Synthetic division to find the 3 zeros of \"x%5E3%2B7x%5E2%2B2x-40=0\"
\n" ); document.write( "

Algebra.Com's Answer #90266 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
\r
\n" ); document.write( "\n" ); document.write( "Any rational zero can be found through this equation\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " where p and q are the factors of the last and first coefficients\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So let's list the factors of -40 (the last coefficient):\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now let's list the factors of 1 (the first coefficient):\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now let's divide each factor of the last coefficient by each factor of the first coefficient\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now simplify\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "These are all the distinct rational zeros of the function that could occur\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "To save time, I'm only going to use synthetic division on the possible zeros that are actually zeros of the function.
\n" ); document.write( "Otherwise, I would have to use synthetic division on every possible root (there are 16 possible roots, so that means there would be at most 16 synthetic division tables).
\n" ); document.write( "However, you might be required to follow this procedure, so this is why I'm showing you how to set up a problem like this\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "When you graph this polynomial, you will see that \"x=2\" is a zero. So we'll use this for the synthetic division \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now set up the synthetic division table by placing the zero in the upper left corner and placing the coefficients of the polynomial to the right of the test zero.\n" ); document.write( "\n" ); document.write( "
2|172-40
|
\r
\n" ); document.write( "\n" ); document.write( "Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 1)\r
\n" ); document.write( "\n" ); document.write( "\n" ); document.write( "\n" ); document.write( "
2|172-40
|
1
\r
\n" ); document.write( "\n" ); document.write( " Multiply 2 by 1 and place the product (which is 2) right underneath the second coefficient (which is 7)\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
2|172-40
|2
1
\r
\n" ); document.write( "\n" ); document.write( " Add 2 and 7 to get 9. Place the sum right underneath 2.\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
2|172-40
|2
19
\r
\n" ); document.write( "\n" ); document.write( " Multiply 2 by 9 and place the product (which is 18) right underneath the third coefficient (which is 2)\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
2|172-40
|218
19
\r
\n" ); document.write( "\n" ); document.write( " Add 18 and 2 to get 20. Place the sum right underneath 18.\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
2|172-40
|218
1920
\r
\n" ); document.write( "\n" ); document.write( " Multiply 2 by 20 and place the product (which is 40) right underneath the fourth coefficient (which is -40)\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
2|172-40
|21840
1920
\r
\n" ); document.write( "\n" ); document.write( " Add 40 and -40 to get 0. Place the sum right underneath 40.\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
2|172-40
|21840
19200
\r
\n" ); document.write( "\n" ); document.write( "Since the last column adds to zero, we have a remainder of zero. This means \"x-2\" is a factor of \"x%5E3+%2B+7x%5E2+%2B+2x+-+40\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now lets look at the bottom row of coefficients:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "The first 3 coefficients (1,9,20) form the quotient\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x%5E2+%2B+9x+%2B+20\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So \"%28x%5E3+%2B+7x%5E2+%2B+2x+-+40%29%2F%28x-2%29=x%5E2+%2B+9x+%2B+20\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "You can use this online polynomial division calculator to check your work\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Basically \"x%5E3+%2B+7x%5E2+%2B+2x+-+40\" factors to \"%28x-2%29%28x%5E2+%2B+9x+%2B+20%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now lets break \"x%5E2+%2B+9x+%2B+20\" down further\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Looking at \"x%5E2%2B9x%2B20\" we can see that the first term is \"x%5E2\" and the last term is \"20\" where the coefficients are 1 and 20 respectively.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now multiply the first coefficient 1 and the last coefficient 20 to get 20. Now what two numbers multiply to 20 and add to the middle coefficient 9? Let's list all of the factors of 20:\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Factors of 20:\r
\n" ); document.write( "\n" ); document.write( "1,2,4,5,10,20\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "-1,-2,-4,-5,-10,-20 ...List the negative factors as well. This will allow us to find all possible combinations\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "These factors pair up and multiply to 20\r
\n" ); document.write( "\n" ); document.write( "1*20\r
\n" ); document.write( "\n" ); document.write( "2*10\r
\n" ); document.write( "\n" ); document.write( "4*5\r
\n" ); document.write( "\n" ); document.write( "(-1)*(-20)\r
\n" ); document.write( "\n" ); document.write( "(-2)*(-10)\r
\n" ); document.write( "\n" ); document.write( "(-4)*(-5)\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "note: remember two negative numbers multiplied together make a positive number\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now which of these pairs add to 9? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to 9\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\n" ); document.write( "\n" ); document.write( "
First NumberSecond NumberSum
1201+20=21
2102+10=12
454+5=9
-1-20-1+(-20)=-21
-2-10-2+(-10)=-12
-4-5-4+(-5)=-9
\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "From this list we can see that 4 and 5 add up to 9 and multiply to 20\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now looking at the expression \"1x%5E2%2B9x%2B20\", replace \"9x\" with \"4x%2B5x\" (notice \"4x%2B5x\" adds up to \"9x\". So it is equivalent to \"9x\")\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x%5E2%2Bhighlight%284x%2B5x%29%2B20\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now let's factor \"1x%5E2%2B4x%2B5x%2B20\" by grouping:\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%28x%5E2%2B4x%29%2B%285x%2B20%29\" Group like terms\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x%28x%2B4%29%2B5%28x%2B4%29\" Factor out the GCF of \"x\" out of the first group. Factor out the GCF of \"5\" out of the second group\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%28x%2B5%29%28x%2B4%29\" Since we have a common term of \"x%2B4\", we can combine like terms\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So \"x%5E2%2B9x%2B20\" factors to \"%28x%2B5%29%28x%2B4%29\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"%28x-2%29%28x%2B5%29%28x%2B4%29\" Now reintroduce the factor \"x-2\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now set each factor equal to zero:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x-2=0\", \"x%2B5=0\" or \"x%2B4=0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now solve for x for each factor:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=2\", \"x=-5\" or \"x=-4\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "------------------------------------------------------------\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " Answer:\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So the zeros of \"x%5E3%2B7x%5E2%2B2x-40\" are \"x=2\", \"x=-5\" or \"x=-4\"\r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );