document.write( "Question 695305: \"x%5E2%2B14xy%2B45y%5E2\" \n" ); document.write( "
Algebra.Com's Answer #428404 by jim_thompson5910(35256)\"\" \"About 
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\n" ); document.write( "\n" ); document.write( "Looking at the expression \"x%5E2%2B14xy%2B45y%5E2\", we can see that the first coefficient is \"1\", the second coefficient is \"14\", and the last coefficient is \"45\".\r
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\n" ); document.write( "\n" ); document.write( "Now multiply the first coefficient \"1\" by the last coefficient \"45\" to get \"%281%29%2845%29=45\".\r
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\n" ); document.write( "\n" ); document.write( "Now the question is: what two whole numbers multiply to \"45\" (the previous product) and add to the second coefficient \"14\"?\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 \"45\" (the previous product).\r
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\n" ); document.write( "\n" ); document.write( "Factors of \"45\":\r
\n" ); document.write( "\n" ); document.write( "1,3,5,9,15,45\r
\n" ); document.write( "\n" ); document.write( "-1,-3,-5,-9,-15,-45\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 \"45\".\r
\n" ); document.write( "\n" ); document.write( "1*45 = 45
\n" ); document.write( "3*15 = 45
\n" ); document.write( "5*9 = 45
\n" ); document.write( "(-1)*(-45) = 45
\n" ); document.write( "(-3)*(-15) = 45
\n" ); document.write( "(-5)*(-9) = 45\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 \"14\":\r
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First NumberSecond NumberSum
1451+45=46
3153+15=18
595+9=14
-1-45-1+(-45)=-46
-3-15-3+(-15)=-18
-5-9-5+(-9)=-14
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\n" ); document.write( "\n" ); document.write( "From the table, we can see that the two numbers \"5\" and \"9\" add to \"14\" (the middle coefficient).\r
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\n" ); document.write( "\n" ); document.write( "So the two numbers \"5\" and \"9\" both multiply to \"45\" and add to \"14\"\r
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\n" ); document.write( "\n" ); document.write( "Now replace the middle term \"14xy\" with \"5xy%2B9xy\". Remember, \"5\" and \"9\" add to \"14\". So this shows us that \"5xy%2B9xy=14xy\".\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2%2Bhighlight%285xy%2B9xy%29%2B45y%5E2\" Replace the second term \"14xy\" with \"5xy%2B9xy\".\r
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\n" ); document.write( "\n" ); document.write( "\"%28x%5E2%2B5xy%29%2B%289xy%2B45y%5E2%29\" Group the terms into two pairs.\r
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\n" ); document.write( "\n" ); document.write( "\"x%28x%2B5y%29%2B%289xy%2B45y%5E2%29\" Factor out the GCF \"x\" from the first group.\r
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\n" ); document.write( "\n" ); document.write( "\"x%28x%2B5y%29%2B9y%28x%2B5y%29\" Factor out \"9y\" 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( "\"%28x%2B9y%29%28x%2B5y%29\" Combine like terms. Or factor out the common term \"x%2B5y\"\r
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\n" ); document.write( "\n" ); document.write( "Answer:\r
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\n" ); document.write( "\n" ); document.write( "So \"x%5E2%2B14xy%2B45y%5E2\" factors to \"%28x%2B9y%29%28x%2B5y%29\".\r
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\n" ); document.write( "\n" ); document.write( "In other words, \"x%5E2%2B14xy%2B45y%5E2=%28x%2B9y%29%28x%2B5y%29\".\r
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\n" ); document.write( "\n" ); document.write( "Note: you can check the answer by expanding \"%28x%2B9y%29%28x%2B5y%29\" to get \"x%5E2%2B14xy%2B45y%5E2\" or by graphing the original expression and the answer (the two graphs should be identical).
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