document.write( "Question 630633: Solve by completing the square what value should you add to each side of the equation x^2+18x=-9 \n" ); document.write( "

Algebra.Com's Answer #397055 by Edwin McCravy(20056) $\"\"$ $\"About$

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document.write( "x² + 18x = -9\r\n" );
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document.write( "Rule for finding the number to add  to both sides to complete the square:\r\n" );
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document.write( "1. Multiply the coefficient of x by \r\n" );
document.write( "2. Square the result of step 1.\r\n" );
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document.write( "The coefficient of x is 18\r\n" );
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document.write( "1. 18· = 9\r\n" );
document.write( "2. 9² = 81\r\n" );
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document.write( "So we must add 81 to both sides\r\n" );
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document.write( "That's all you were asked for.\r\n" );
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document.write( "To solve the equation,\r\n" );
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document.write( "x² + 18x = -9\r\n" );
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document.write( "add 81 to both sides:\r\n" );
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document.write( "x² + 18x + 81 = -9 + 81\r\n" );
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document.write( "Factor the left side\r\n" );
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document.write( "(x + 9)(x + 9) = 72\r\n" );
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document.write( "Write the left side as the square of a binomial:\r\n" );
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document.write( "(x + 9)² = 72\r\n" );
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document.write( "Use the principle of square roots.  \r\n" );
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document.write( "1. Eliminate the square and the parentheses on the left.\r\n" );
document.write( "2. Take ± the square roots of the right side:\r\n" );
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document.write( "  x + 9 = \r\n" );
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document.write( "  x + 9 = \r\n" );
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document.write( "  x + 9 = \r\n" );
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document.write( "      x = -9 ± 6\r\n" );
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document.write( "Two solutions:\r\n" );
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document.write( "       x = -9 + 6 and       x = -9 - 6\r\n" );
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document.write( " Edwin

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