document.write( "Question 371941: Solve the following logarithmic equation. Check all solutions.
\n" ); document.write( "log(x)+log(x+21)=2 \n" ); document.write( "

Algebra.Com's Answer #264953 by nerdybill(7384) $\"\"$ $\"About$

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log(x)+log(x+21)=2
\n" ); document.write( "log(x(x+21))=2
\n" ); document.write( "x(x+21) = 10^2
\n" ); document.write( "x^2+21x = 100
\n" ); document.write( "x^2+21x-100 = 0
\n" ); document.write( "Factoring the left:
\n" ); document.write( "(x+25)(x-4) = 0
\n" ); document.write( ".
\n" ); document.write( "x = {-25, 4}
\n" ); document.write( "We can throw out the -25 solution -- it is an extraneous solution leaving:
\n" ); document.write( "x = 4\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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