document.write( "Question 665588: In solving the equation (x + 4)(x – 4) = 9, Eric stated that the solution would be
\n" ); document.write( "x + 4 = 9 => x = 5
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\n" ); document.write( "(x – 4) = 9 => x = 13
\n" ); document.write( "However, at least one of these solutions fails to work when substituted back into the original equation. Why is that? Please help Eric to understand better; solve the problem yourself, and explain your reasoning.
\n" ); document.write( "please help me! \n" ); document.write( "

Algebra.Com's Answer #413938 by ewatrrr(24785) $\"\"$ $\"About$

You can put this solution on YOUR website!

 
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document.write( "Hi,
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document.write( "The Idea is   (x + 4)(x – 4) = 9    needs to be set to ZERO to solve for x.
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document.write( " (x + 4)(x – 4) = 9
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document.write( "x^2 - 16 = 9
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document.write( "  x^2 - 25 = 0    || Now it is in a format to solve for x
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document.write( " (x-5)(x+5) = 0
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document.write( " (x-5) = 0,  x = 5
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document.write( "0r (x+5) = 0, x = -5 \n" );
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