document.write( "Question 87641: If a^2+b^2 = 7ab, show that log a+b/3=1/2 (loga + logb) \n" ); document.write( "
Algebra.Com's Answer #63556 by longjonsilver(2297)\"\" \"About 
You can put this solution on YOUR website!
Starting with \"+log%28%28a%2Bb%29%2F3%29+=+%281%2F2%29%28loga+%2B+logb%29+\" i shall re-write it as \"+2log%28%28a%2Bb%29%2F3%29+=+%28loga+%2B+logb%29+\".\r
\n" ); document.write( "\n" ); document.write( "I am going to prove this is correct instead by looking at the Left hand side \"+2log%28%28a%2Bb%29%2F3%29+\" and showing that it equals the right hand side \"+%28loga+%2B+logb%29+\".\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So,
\n" ); document.write( "\"+2log%28%28a%2Bb%29%2F3%29+\"
\n" ); document.write( "\"+log%28%28%28a%2Bb%29%2F3%29%29%5E2+\" --> one of laws of Logs
\n" ); document.write( "\"+log%28%28a%5E2%2B2ab%2Bb%5E2%29%2F9%29+\" --> multiply out brackets\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "now we are told that \"+a%5E2%2Bb%5E2+=+7ab+\" so sub that into what we have and we get:
\n" ); document.write( "\"+log%28%28a%5E2%2Bb%5E2%2B2ab%29%2F9%29+\" re-arrange order so you can see the squared terms together
\n" ); document.write( "\"+log%28%287ab%2B2ab%29%2F9%29+\" --> sub in the other equality
\n" ); document.write( "\"+log%28%289ab%29%2F9%29+\" --> add together like terms
\n" ); document.write( "\"+log%28ab%29+\" --> cancel out the 9's
\n" ); document.write( "\"+log%28a%29+%2B+log%28b%29+\" use one of the Laws of Logs\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "which is what i set out to prove it equalled.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "cheers
\n" ); document.write( "jon
\n" ); document.write( "
\n" ); document.write( "
\n" );