document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1074799>Question 1074799</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Justin recently drove to visit his parents who live 864 miles away. On hi way there his average speed was 21 miles per hour faster than on his way home. If Justin spent a total of 24 hours driving, find the two rates. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #689474 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=689474\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> speed there was x+21 mph and time was 864/x+21hours. S*t=distance<BR>\n" );
document.write( "speed back was (x) mph and time was 864/x hours.<BR>\n" );
document.write( "The two times add to 24<BR>\n" );
document.write( "so 864/x+864/(x+21)=24<BR>\n" );
document.write( "multiply both sides by x(x+21)<BR>\n" );
document.write( "864(x+21)+864(x)=24(x(x+21))<BR>\n" );
document.write( "864x+18144+864x=24x^2+504x<BR>\n" );
document.write( "0=24x^2-1224x-18144<BR>\n" );
document.write( "divide by 24<BR>\n" );
document.write( "x^2-51x-756=0<BR>\n" );
document.write( "(x-63)(x+12)=0<BR>\n" );
document.write( "x=63 mph, only positive root speed back, which took 864/63 or 13.71 hours.<BR>\n" );
document.write( "x+21=84 mph, which took 10.29 hours there.<BR>\n" );
document.write( "Total is 24 hours.<BR>\n" );
document.write( " </SPAN>\n" );
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