document.write( "Question 557496: 25^x + 2 * 5^x = 15 \n" ); document.write( "

Algebra.Com's Answer #362769 by lwsshak3(11628) $\"\"$ $\"About$

You can put this solution on YOUR website!
25^x + 2 * 5^x = 15
\n" ); document.write( "25^x=5^2x
\n" ); document.write( "..
\n" ); document.write( "5^2x+2*5^x-15=0
\n" ); document.write( "..
\n" ); document.write( "let u=5^x
\n" ); document.write( "u^2=5^2x
\n" ); document.write( "u^2+2u-15=0
\n" ); document.write( "(u+5)(u-3)=0
\n" ); document.write( "u=-5
\n" ); document.write( "or
\n" ); document.write( "u=3
\n" ); document.write( "..
\n" ); document.write( "For u=-5
\n" ); document.write( "5^x≠-5 (reject, 5^x>0)
\n" ); document.write( "..
\n" ); document.write( "For u=3
\n" ); document.write( "5^x=3
\n" ); document.write( "take log of both sides
\n" ); document.write( "xlog5=log3
\n" ); document.write( "x=log3/log5≈0.6826 \n" ); document.write( "

\n" );