document.write( "Question 151058: please help me solve this problem using the quadratic root formula: \"x%5E2-x%2B20=0\" \n" ); document.write( "
Algebra.Com's Answer #110974 by jim_thompson5910(35256)\"\" \"About 
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\n" ); document.write( "\"x%5E2-x%2B20=0\" Start with the given equation.\r
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\n" ); document.write( "\n" ); document.write( "Notice we have a quadratic equation in the form of \"ax%5E2%2Bbx%2Bc\" where \"a=1\", \"b=-1\", and \"c=20\"\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-%28-1%29+%2B-+sqrt%28+%28-1%29%5E2-4%281%29%2820%29+%29%29%2F%282%281%29%29\" Plug in \"a=1\", \"b=-1\", and \"c=20\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+%28-1%29%5E2-4%281%29%2820%29+%29%29%2F%282%281%29%29\" Negate \"-1\" to get \"1\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+1-4%281%29%2820%29+%29%29%2F%282%281%29%29\" Square \"-1\" to get \"1\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+1-80+%29%29%2F%282%281%29%29\" Multiply \"4%281%29%2820%29\" to get \"80\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+-79+%29%29%2F%282%281%29%29\" Subtract \"80\" from \"1\" to get \"-79\"\r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+sqrt%28+-79+%29%29%2F%282%29\" Multiply \"2\" and \"1\" to get \"2\". \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281+%2B-+i%2Asqrt%2879%29%29%2F%282%29\" Simplify the square root \r
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\n" ); document.write( "\n" ); document.write( "\"x+=+%281%2Bi%2Asqrt%2879%29%29%2F%282%29\" or \"x+=+%281-i%2Asqrt%2879%29%29%2F%282%29\" Break up the expression. \r
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\n" ); document.write( "\n" ); document.write( "So our answers are \"x+=+%281%2Bi%2Asqrt%2879%29%29%2F%282%29\" or \"x+=+%281-i%2Asqrt%2879%29%29%2F%282%29\" \r
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\n" ); document.write( "\n" ); document.write( "which approximate to \"x=0.5%2B4.444%2Ai\" or \"x=0.5-4.444%2Ai\"
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