document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=236860>Question 236860</A>: <I><SPAN STYLE=\"word-break: break-all;\"> the height of an object projected upward from ground level is given by h+-16t^2+128t where h is in feet and t is time in seconds. when will the object be 240 feet above ground level ...\r<BR>\n" );
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document.write( "please help i dont understand </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #174236 by </B><A HREF=/tutors/aboutme.mpl?userid=Earlsdon><B>Earlsdon(6294)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Earlsdon><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=174236\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Starting with the given function:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=h%28t%29+=+-16t%5E2%2B128t ALIGN=MIDDLE  ALT=\"h%28t%29+=+-16t%5E2%2B128t\"   DISABLED_style= \"max-width:90%; height:auto;\" > you are being asked...\"at what time, t, will h(t) = 240 ft.\"<BR>\n" );
document.write( "So you set h(t) = 240 and solve for t.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=240+=+-16t%5E2%2B128t ALIGN=MIDDLE  ALT=\"240+=+-16t%5E2%2B128t\"   DISABLED_style= \"max-width:90%; height:auto;\" > Subtract 240 from both sides and rearrange a bit.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-16t%5E2%2B128t-240+=+0 ALIGN=MIDDLE  ALT=\"-16t%5E2%2B128t-240+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" > Now you have a quadratic equation that can be solved by various methods.<BR>\n" );
document.write( "I would factor -16 first just to simplify the calculations a bit.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-16%28t%5E2-8t%2B15%29+=+0 ALIGN=MIDDLE  ALT=\"-16%28t%5E2-8t%2B15%29+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" > Notice the change of signs when we factored the -16!<BR>\n" );
document.write( "Now, from the zero product rule, you get:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%5E2-8t%2B15+=+0 ALIGN=MIDDLE  ALT=\"t%5E2-8t%2B15+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" > This can be solved by factoring.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28t-3%29%28t-5%29+=+0 ALIGN=MIDDLE  ALT=\"%28t-3%29%28t-5%29+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" > Apply the zero product rule again.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t-3+=+0 ALIGN=MIDDLE  ALT=\"t-3+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" > or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t-5+=+0 ALIGN=MIDDLE  ALT=\"t-5+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" > so that...<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+3 ALIGN=MIDDLE  ALT=\"t+=+3\"   DISABLED_style= \"max-width:90%; height:auto;\" > or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+5 ALIGN=MIDDLE  ALT=\"t+=+5\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Why are there two answers?<BR>\n" );
document.write( "On the way up, the object will reach 240 feet in 3 seconds (t = 3).<BR>\n" );
document.write( "On the way down, the object will again pass the 240-foot level in 5 seconds (t = 5).<BR>\n" );
document.write( "Does this all make sense to you? </SPAN>\n" );
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