document.write( "Question 481620: Solve for x: \r
\n" ); document.write( "\n" ); document.write( "2^2x - 3 * 2^x - 40 = 0 \n" ); document.write( "

Algebra.Com's Answer #329779 by Gogonati(855) $\"\"$ $\"About$

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$\"2%5E%282x%29-3%2A2%5Ex-40=0\"$ , substituting $\"2%5Ex=y\"$ we get the quadratic equation:\r
\n" ); document.write( "\n" ); document.write( " $\"y%5E2-3y-40=0\"$ . We solve this equation by factoring: $\"%28y-8%29%28y%2B5%29=0\"$ \r
\n" ); document.write( "\n" ); document.write( "The roots are: {-5, 8}. Now we find the roots of original equation:\r
\n" ); document.write( "\n" ); document.write( " $\"2%5Ex=8\"$ <=> $\"x=3\"$ and $\"2%5Ex=-5\"$ <=> $\"x%2Aln2=ln%28-5%29\"$ , since the log of \r
\n" ); document.write( "\n" ); document.write( "negative numbers doesn't exist our equation has only one solution x=3. \n" ); document.write( "

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