document.write( "Question 972361: solve for x
\n" ); document.write( "3^2x - 9(3^-2x) = 8 \n" ); document.write( "

Algebra.Com's Answer #594698 by Alan3354(69443) $\"\"$ $\"About$

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solve for x
\n" ); document.write( "3^2x - 9(3^-2x) = 8
\n" ); document.write( "-----
\n" ); document.write( "3^2x - 3^(-2x+2) = 8
\n" ); document.write( "3^(4x) - 3^2 = 8*3^(2x)
\n" ); document.write( "3^(4x) -8*3^(2x) - 3^2 = 0
\n" ); document.write( "Sub u for 3^2x
\n" ); document.write( "----
\n" ); document.write( "u^2 - 8u - 9 = 0
\n" ); document.write( "(u - 9)*(u + 1) = 0
\n" ); document.write( "-------------
\n" ); document.write( "u = 9 --> x = 1
\n" ); document.write( "==================
\n" ); document.write( "u = -1 extraneous, ignore \n" ); document.write( "

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