document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=433527>Question 433527</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Use the \"change of base\" formula to find: log7 21 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #300509 by </B><A HREF=/tutors/aboutme.mpl?userid=belle3833><B>belle3833(46)</B></A><img src=\"/images/stars/stars-07.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=belle3833><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=belle3833><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=300509\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Change of Base Formula\r<BR>\n" );
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document.write( "logc(a)=logb(a)/logb(c)\r<BR>\n" );
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document.write( "b is the new base that we are changing it to.  For our purposes (determining a decimal value), this new base can be either 10 or e.  \r<BR>\n" );
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document.write( "For our particular example , c = 7and a = 21.  We will first change to base 10.  So b will be 10.  This will give us \r<BR>\n" );
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document.write( "log7(21)=log10(21)/log10(7)<BR>\n" );
document.write( "Plug this into your calculator to find the decimal value. 1.95\r<BR>\n" );
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document.write( "We could also choose to change to base e.  This would give us c = 7 , a = 21, andb = e.  We would get .  You will see that when you plug this into your calculator, you will get thesame decimal answers as with the change to base 10.\r<BR>\n" );
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