document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=724451>Question 724451</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An object's height, in meters, when thrown vertically from the ground at a velocity of 80m/s is given by the equation H=-4.9t^2+80t. Ignoring wind resistance, how many seconds will it take the object to return to the ground? in other words, when is H=0? \r<BR>\n" );
document.write( "\n" );
document.write( "In this problem, I set the equation equal to 0 then I used the quadratic formula but that was wrong....HELP PLEASE!!! </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #443761 by </B><A HREF=/tutors/aboutme.mpl?userid=jsmallt9><B>jsmallt9(3758)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jsmallt9><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=443761\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> If you use the formula correctly then you can't get the wrong answer.<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=0+=+-4.9t%5E2+%2B+80t ALIGN=MIDDLE  ALT=\"0+=+-4.9t%5E2+%2B+80t\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "a = -4.9<BR>\n" );
document.write( "b = 80<BR>\n" );
document.write( "c = 0<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-%2880%29%2B-sqrt%28%2880%29%5E2-4%28-4.9%29%280%29%29%29%2F2%28-4.9%29 ALIGN=MIDDLE  ALT=\"t+=+%28-%2880%29%2B-sqrt%28%2880%29%5E2-4%28-4.9%29%280%29%29%29%2F2%28-4.9%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-%2880%29%2B-sqrt%286400-4%28-4.9%29%280%29%29%29%2F2%28-4.9%29 ALIGN=MIDDLE  ALT=\"t+=+%28-%2880%29%2B-sqrt%286400-4%28-4.9%29%280%29%29%29%2F2%28-4.9%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-%2880%29%2B-sqrt%286400-0%29%29%2F2%28-4.9%29 ALIGN=MIDDLE  ALT=\"t+=+%28-%2880%29%2B-sqrt%286400-0%29%29%2F2%28-4.9%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-%2880%29%2B-sqrt%286400%29%29%2F2%28-4.9%29 ALIGN=MIDDLE  ALT=\"t+=+%28-%2880%29%2B-sqrt%286400%29%29%2F2%28-4.9%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-%2880%29%2B-80%29%2F2%28-4.9%29 ALIGN=MIDDLE  ALT=\"t+=+%28-%2880%29%2B-80%29%2F2%28-4.9%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-80+%2B-+80%29%2F%28-9.8%29 ALIGN=MIDDLE  ALT=\"t+=+%28-80+%2B-+80%29%2F%28-9.8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "which is short for:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-80+%2B+80%29%2F%28-9.8%29 ALIGN=MIDDLE  ALT=\"t+=+%28-80+%2B+80%29%2F%28-9.8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-80+-+80%29%2F%28-9.8%29 ALIGN=MIDDLE  ALT=\"t+=+%28-80+-+80%29%2F%28-9.8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+0%2F%28-9.8%29 ALIGN=MIDDLE  ALT=\"t+=+0%2F%28-9.8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-160%29%2F%28-9.8%29 ALIGN=MIDDLE  ALT=\"t+=+%28-160%29%2F%28-9.8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+0 ALIGN=MIDDLE  ALT=\"t+=+0\"   DISABLED_style= \"max-width:90%; height:auto;\" > or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+800%2F49 ALIGN=MIDDLE  ALT=\"t+=+800%2F49\"   DISABLED_style= \"max-width:90%; height:auto;\" > (or approximately 16.326530612244897959183673469388)<BR>\n" );
document.write( "The answer of zero reflects the fact that the object started on the ground. The other answer is the one you are looking for.<br><BR>\n" );
document.write( "Of course this problem did not need the quadratic formula. The right side of<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=0+=+-4.9t%5E2+%2B+80t ALIGN=MIDDLE  ALT=\"0+=+-4.9t%5E2+%2B+80t\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "factors!<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=0+=+t%28-4.9t+%2B+80%29 ALIGN=MIDDLE  ALT=\"0+=+t%28-4.9t+%2B+80%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "From the Zero Product Property:<BR>\n" );
document.write( "t = 0 or -4.9t + 80 = 0<BR>\n" );
document.write( "Solving the second one:<BR>\n" );
document.write( "t = 0 or t = 800/49<br><BR>\n" );
document.write( "It's much easier to solve these if you can factor them. The formula is complicated and mistakes can easily be made. (You must have made a mistake yourself if you didn't get the right answer.) </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );