document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=672615>Question 672615</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A bicyclist is riding at a speed of 18mi/h when she starts down a long hill. The distance d she travels in feet can be modeled by d(t) = 4t^2 + 18t, where t is the time in seconds. How long will it take her to reach the bottom of a 400-foot-long hill?\r<BR>\n" );
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document.write( "We have to use the quadratic formula to find t.<BR>\n" );
document.write( "I attempted the problem and i got 12.5 seconds.. but im not sure if im right<BR>\n" );
document.write( "Heres my work:<BR>\n" );
document.write( "d(t)=4t^2+18t=400<BR>\n" );
document.write( "d(t)=4t^2+18t=400/4<BR>\n" );
document.write( "t^2+4.5t=100<BR>\n" );
document.write( "t^2+4.5t-100=0<BR>\n" );
document.write( "(x-12.5)(x+8)<BR>\n" );
document.write( "12.5 & -8 seconds.\r<BR>\n" );
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document.write( "is this correct?<BR>\n" );
document.write( "Thanks(: </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #418216 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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=418216\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> You should have 8 or -12.5 seconds.\r<BR>\n" );
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document.write( "Because a negative amount of time doesn't make sense, you toss out the negative solution to get t = 8 seconds. </SPAN>\n" );
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