document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1168696>Question 1168696</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If 9^y = x, which of the following represents 9^y - 9^(y-3) :\r<BR>\n" );
document.write( "\n" );
document.write( "A) 1/ x^3<BR>\n" );
document.write( "B) x^3<BR>\n" );
document.write( "C) 729x<BR>\n" );
document.write( "D) 729/728 x<BR>\n" );
document.write( "E) 728/729 x<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #793292 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=793292\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> your expression is 9^y - 9^(y-3)<BR>\n" );
document.write( "this is equivalent to 9^y - 9^y/(9^3)<BR>\n" );
document.write( "since 9^3 = 729, this becomes:<BR>\n" );
document.write( "9^y - 9^y/729<BR>\n" );
document.write( "since 9^y = x, this becomes:<BR>\n" );
document.write( "x - x/729<BR>\n" );
document.write( "put everything under a common denominator and you get:<BR>\n" );
document.write( "(729*x - x)/729 which becomes:<BR>\n" );
document.write( "728*x / 729 which can be shown as:<BR>\n" );
document.write( "728/729 * x.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "this looks like selection E.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "to confirm, let y be any value.<BR>\n" );
document.write( "i chose 5.<BR>\n" );
document.write( "when y = 5, x = 9^5 = 59049<BR>\n" );
document.write( "728/729 * x = 58968<BR>\n" );
document.write( "9^5 - 9^(5-3) = 9^5 - 9^2 = 58968<BR>\n" );
document.write( "they're the same, confirming the solution is correct.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "go with selection E.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );