document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1146849>Question 1146849</A>: <I><SPAN STYLE=\"word-break: break-all;\"> the variable interest rate on a student loan changes each july 1 based on the bank prime loan rate.For the years 1992-2007 this rate can be approximated by the model r(x)= -0.115x^2+1.183x+5.623 where x is the number of years since 1992 and r is the interest rate as a percent <BR>\n" );
document.write( "calculate the highest rate during this time period during which year was the interest rate the highest <BR>\n" );
document.write( "use graph to estimate the rate in 2010 does the value seem reasonable? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #768210 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><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=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=768210\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "(1) Graph the equation on a graphing calculator.<br><BR>\n" );
document.write( "(2) Find the maximum value of the function, and the x value which produces that maximum.  1992 plus the x value is the year in which the interest rate is highest.<br><BR>\n" );
document.write( "(3) Evaluate the function for x = 18 (2010 is 18 years after 1992).  The function value is negative there.  Is that reasonable?<br><BR>\n" );
document.write( "Note that the problem says the given function is only applicable for the years 1992-2007; so using it to estimate the interest rate in 2010 might not be valid.  However, even for the year 2007 (x=15), the function value is negative; so the function is not realistic. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );