document.write( "Question 135305: Solve for x: 2(8)^(4x)-33(8)^(2x)+16=0 \n" ); document.write( "
Algebra.Com's Answer #99156 by Earlsdon(6294)\"\" \"About 
You can put this solution on YOUR website!
Solve for x:
\n" ); document.write( "\"2%288%29%5E%284x%29-33%288%29%5E%282x%29%2B16+=+0\"
\n" ); document.write( "Let's temporarily substitute \"z+=+%288%29%5E%282x%29\" and \"z%5E2+=+%288%29%5E%284x%29\"
\n" ); document.write( "\"2z%5E2-33z%2B16+=+0\" This can be solved for z by factoring.
\n" ); document.write( "\"%282z-1%29%28z-16%29+=+0\" and...
\n" ); document.write( "\"2z-1+=+0\" and \"z-16+=+0\", so we have...
\n" ); document.write( "\"2z+=+1\" so that:
\n" ); document.write( "\"z+=+1%2F2\" and
\n" ); document.write( "\"z+=+16\"
\n" ); document.write( "Now we replace the z with \"z+=+%288%29%5E%282x%29\", so...
\n" ); document.write( "\"%288%29%5E%282x%29+=+1%2F2\" but \"8+=+2%5E3\" and \"1%2F2+=+2%5E%28-1%29\", so, making these substitutions, we get:
\n" ); document.write( "\"%282%5E3%29%5E%282x%29+=+%282%29%5E%28-1%29\" Simplify the left side.
\n" ); document.write( "\"%282%29%5E%286x%29+=+%282%29%5E%28-1%29\" Applying the rule: If\"m%5Ea+=+m%5Eb\" then \"a+=+b\", so...
\n" ); document.write( "\"6x+=+-1\" Divide both sides by 6.
\n" ); document.write( "\"x+=+-1%2F6\" This is one of the roots.
\n" ); document.write( "\"z+=+16\" Substitute \"z+=+%288%29%5E%282x%29\"
\n" ); document.write( "\"%288%29%5E%282x%29+=+16\" Substitute: \"8+=+2%5E3\" and \"16+=+2%5E4\"
\n" ); document.write( "\"%282%5E3%29%5E%282x%29+=+%282%29%5E4\" Simplify the left side.
\n" ); document.write( "\"%282%29%5E%286x%29+=+%282%29%5E4\" or...
\n" ); document.write( "\"6x+=+4\" Divide both sides by 6.
\n" ); document.write( "\"x+=+4%2F6\" Simplify.
\n" ); document.write( "\"x+=+2%2F3\" This is the second root.
\n" ); document.write( "Solution is:
\n" ); document.write( "\"x+=+-1%2F6\"
\n" ); document.write( "\"x+=+2%2F3\"\r
\n" ); document.write( "\n" ); document.write( "I'll leave the check for you to do. It's not difficult and I've done it myself and the two solutions for x are indeed valid!
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