document.write( "Question 200535: 8x^2-10x-3= \n" ); document.write( "

Algebra.Com's Answer #150776 by jim_thompson5910(35256) $\"\"$ $\"About$

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\n" ); document.write( "Looking at the expression $\"8x%5E2-10x-3\"$ , we can see that the first coefficient is $\"8\"$ , the second coefficient is $\"-10\"$ , and the last term is $\"-3\"$ .\r
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\n" ); document.write( "\n" ); document.write( "Now multiply the first coefficient $\"8\"$ by the last term $\"-3\"$ to get $\"%288%29%28-3%29=-24\"$ .\r
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\n" ); document.write( "\n" ); document.write( "Now the question is: what two whole numbers multiply to $\"-24\"$ (the previous product) and add to the second coefficient $\"-10\"$ ?\r
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\n" ); document.write( "\n" ); document.write( "To find these two numbers, we need to list all of the factors of $\"-24\"$ (the previous product).\r
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\n" ); document.write( "\n" ); document.write( "Factors of $\"-24\"$ :\r
\n" ); document.write( "\n" ); document.write( "1,2,3,4,6,8,12,24\r
\n" ); document.write( "\n" ); document.write( "-1,-2,-3,-4,-6,-8,-12,-24\r
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\n" ); document.write( "\n" ); document.write( "Note: list the negative of each factor. This will allow us to find all possible combinations.\r
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\n" ); document.write( "\n" ); document.write( "These factors pair up and multiply to $\"-24\"$ .\r
\n" ); document.write( "\n" ); document.write( "1*(-24)
\n" ); document.write( "2*(-12)
\n" ); document.write( "3*(-8)
\n" ); document.write( "4*(-6)
\n" ); document.write( "(-1)*(24)
\n" ); document.write( "(-2)*(12)
\n" ); document.write( "(-3)*(8)
\n" ); document.write( "(-4)*(6)\r
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\n" ); document.write( "\n" ); document.write( "Now let's add up each pair of factors to see if one pair adds to the middle coefficient $\"-10\"$ :\r
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First Number	Second Number	Sum
1	-24	1+(-24)=-23
2	-12	2+(-12)=-10
3	-8	3+(-8)=-5
4	-6	4+(-6)=-2
-1	24	-1+24=23
-2	12	-2+12=10
-3	8	-3+8=5
-4	6	-4+6=2

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\n" ); document.write( "\n" ); document.write( "From the table, we can see that the two numbers $\"2\"$ and $\"-12\"$ add to $\"-10\"$ (the middle coefficient).\r
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\n" ); document.write( "\n" ); document.write( "So the two numbers $\"2\"$ and $\"-12\"$ both multiply to $\"-24\"$ and add to $\"-10\"$ \r
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\n" ); document.write( "\n" ); document.write( "Now replace the middle term $\"-10x\"$ with $\"2x-12x\"$ . Remember, $\"2\"$ and $\"-12\"$ add to $\"-10\"$ . So this shows us that $\"2x-12x=-10x\"$ .\r
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\n" ); document.write( "\n" ); document.write( " $\"8x%5E2%2Bhighlight%282x-12x%29-3\"$ Replace the second term $\"-10x\"$ with $\"2x-12x\"$ .\r
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\n" ); document.write( "\n" ); document.write( " $\"%288x%5E2%2B2x%29%2B%28-12x-3%29\"$ Group the terms into two pairs.\r
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\n" ); document.write( "\n" ); document.write( " $\"2x%284x%2B1%29%2B%28-12x-3%29\"$ Factor out the GCF $\"2x\"$ from the first group.\r
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\n" ); document.write( "\n" ); document.write( " $\"2x%284x%2B1%29-3%284x%2B1%29\"$ Factor out $\"3\"$ from the second group. The goal of this step is to make the terms in the second parenthesis equal to the terms in the first parenthesis.\r
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\n" ); document.write( "\n" ); document.write( " $\"%282x-3%29%284x%2B1%29\"$ Combine like terms. Or factor out the common term $\"4x%2B1\"$ \r
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\n" ); document.write( "\n" ); document.write( "Answer:\r
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\n" ); document.write( "\n" ); document.write( "So $\"8x%5E2-10x-3\"$ factors to $\"%282x-3%29%284x%2B1%29\"$ .\r
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\n" ); document.write( "\n" ); document.write( "Note: you can check the answer by FOILing $\"%282x-3%29%284x%2B1%29\"$ to get $\"8x%5E2-10x-3\"$ or by graphing the original expression and the answer (the two graphs should be identical).\r
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\n" ); document.write( "\n" ); document.write( "If you have any questions, email me at jim_thompson5910@hotmail.com.
\n" ); document.write( "Check out my website if you are interested in tutoring.
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