document.write( "Question 215124: what are the exact solutions x^2+18x+81=16 \n" ); document.write( "
Algebra.Com's Answer #162552 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
There are two ways to do this:\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2%2B18x%2B81=16\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2%2B18x%2B81-16=0\" Get every term to the left side.\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2%2B18x%2B65=0\" Combine like terms.\r
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\n" ); document.write( "\n" ); document.write( "Notice that the quadratic \"x%5E2%2B18x%2B65\" is in the form of \"Ax%5E2%2BBx%2BC\" where \"A=1\", \"B=18\", and \"C=65\"\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-%2818%29+%2B-+sqrt%28+%2818%29%5E2-4%281%29%2865%29+%29%29%2F%282%281%29%29\" Plug in \"A=1\", \"B=18\", and \"C=65\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-18+%2B-+sqrt%28+324-4%281%29%2865%29+%29%29%2F%282%281%29%29\" Square \"18\" to get \"324\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-18+%2B-+sqrt%28+324-260+%29%29%2F%282%281%29%29\" Multiply \"4%281%29%2865%29\" to get \"260\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-18+%2B-+sqrt%28+64+%29%29%2F%282%281%29%29\" Subtract \"260\" from \"324\" to get \"64\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-18+%2B-+sqrt%28+64+%29%29%2F%282%29\" Multiply \"2\" and \"1\" to get \"2\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-18+%2B-+8%29%2F%282%29\" Take the square root of \"64\" to get \"8\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-18+%2B+8%29%2F%282%29\" or \"x+=+%28-18+-+8%29%2F%282%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%28-10%29%2F%282%29\" or \"x+=++%28-26%29%2F%282%29\" Combine like terms. \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+-5\" or \"x+=+-13\" Simplify. \r
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\n" ); document.write( "\n" ); document.write( "So the solutions are \"x+=+-5\" or \"x+=+-13\" \r
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\n" ); document.write( "\n" ); document.write( "Method # 2\r
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\n" ); document.write( "\n" ); document.write( "\"x%5E2%2B18x%2B81=16\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "\"%28x%2B9%29%5E2=16\" Factor the left side\r
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\n" ); document.write( "\n" ); document.write( "\"x%2B9=%22%22%2B-sqrt%2816%29\" Take the square root of both sides.\r
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\n" ); document.write( "\n" ); document.write( "\"x%2B9=sqrt%2816%29\" or \"x%2B9=-sqrt%2816%29\" Break up the \"plus/minus\" to form two equations.\r
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\n" ); document.write( "\n" ); document.write( "\"x%2B9=4\" or \"x%2B9=-4\" Take the square root of \"16\" to get \"4\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=-9%2B4\" or \"x=-9-4\" Subtract \"9\" from both sides.\r
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\n" ); document.write( "\n" ); document.write( "\"x=-5\" or \"x=-13\" Combine like terms.\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 solutions are \"x=-5\" or \"x=-13\" (which is what we got earlier).\r
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