document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=64047>Question 64047</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hello!<BR>\n" );
document.write( "Here is the information I have been given, an explanation of what I need to do, what I understand and what I don't. <BR>\n" );
document.write( "Please help!<BR>\n" );
document.write( "Thanks for looking at this problem!<BR>\n" );
document.write( "Time /Temp<BR>\n" );
document.write( "5 /55.7<BR>\n" );
document.write( "15 /49.1<BR>\n" );
document.write( "25 /42.8<BR>\n" );
document.write( "35 /37<BR>\n" );
document.write( "50 /29.9<BR>\n" );
document.write( "60 /25.8<BR>\n" );
document.write( "70 /22.4<BR>\n" );
document.write( "80 /19.2<BR>\n" );
document.write( "90 /16.4<BR>\n" );
document.write( "100 /14.1<BR>\n" );
document.write( "120 /10.3<BR>\n" );
document.write( "140 /7.4<BR>\n" );
document.write( "150 /6.1<BR>\n" );
document.write( "170 /4<BR>\n" );
document.write( "180 /3.3<BR>\n" );
document.write( "The instructions tell me to calculate a linear regression line and then and from that to write an exponential equation that will match the original data.<BR>\n" );
document.write( "I get how to figure out the linear regression line.<BR>\n" );
document.write( "in <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=a%2Bbx ALIGN=MIDDLE  ALT=\"y=a%2Bbx\"   DISABLED_style= \"max-width:90%; height:auto;\" > form I get <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=y=47.4021-.2879x ALIGN=MIDDLE  ALT=\"y=47.4021-.2879x\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "I don't understand how to derive an exponential equation from this information.<BR>\n" );
document.write( "Thanks Again </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #44689 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=44689\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> One way to get the exponential regression equation is to <BR>\n" );
document.write( "use a calculator with that function programmed into it.<BR>\n" );
document.write( "The TI-83 is such a calculator.<BR>\n" );
document.write( "Using it I get this exponential equation:<BR>\n" );
document.write( "y=(65.59)*(9.984)^x<BR>\n" );
document.write( "-------------<BR>\n" );
document.write( "Another way to proceed:<BR>\n" );
document.write( "Pick two points from your data set:<BR>\n" );
document.write( "(100,14.1) and (35,37)<BR>\n" );
document.write( "The form is y=ab^x<BR>\n" );
document.write( "Each point gives a form:<BR>\n" );
document.write( "14.1=ab^100<BR>\n" );
document.write( "37=ab^35<BR>\n" );
document.write( "------------<BR>\n" );
document.write( "You need to solve for a and for b.<BR>\n" );
document.write( "Divide the 1st by the 2nd to get:<BR>\n" );
document.write( "(14.1/37)=b^65<BR>\n" );
document.write( "Take the 65th root of both sides to get:<BR>\n" );
document.write( "b=0.986....<BR>\n" );
document.write( "Substitute that value into one of the equations to solve for \"a\", as follows:<BR>\n" );
document.write( "37=a(0.986...)^35<BR>\n" );
document.write( "37=a(0.608...)<BR>\n" );
document.write( "EQUATION:<BR>\n" );
document.write( "y=(0.608..)(0.986...)^x<BR>\n" );
document.write( "---------------------------<BR>\n" );
document.write( "You will get a little different equation if you pick <BR>\n" );
document.write( "different points, but you will get an exponential equation.<BR>\n" );
document.write( "--------<BR>\n" );
document.write( "Hope this helps.<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );