document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1172212>Question 1172212</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 4. A rock is thrown off a 75-meter-high cliff into some water. The height of the rock relative to the cliff after t seconds is given by h(t)=−5t2+20t. Show clear solutions thanksss!<BR>\n" );
document.write( "a. Where will the rock be after five seconds?<BR>\n" );
document.write( "b. How long before the rock reaches its maximum height?<BR>\n" );
document.write( "c. When will the rock hit the water?<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #797178 by </B><A HREF=/tutors/aboutme.mpl?userid=Boreal><B>Boreal(15235)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Boreal><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=Boreal><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=797178\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Draw this, and the equation needed from the water is h(t)=-5t^2+20t+75, the height of the cliff.<BR>\n" );
document.write( "after 5 seconds, h(5)=-5*25+20(5)+75=50 m above the water.<BR>\n" );
document.write( "-<BR>\n" );
document.write( "maximum height is at t=-b/2a or -20/-10 or 2 seconds<BR>\n" );
document.write( "-<BR>\n" );
document.write( "it will hit the water when the equation equals 0.<BR>\n" );
document.write( "changing all the signs, 5t^2-20t-75=0<BR>\n" );
document.write( "there is one positive root<BR>\n" );
document.write( "5(t^2-4t-15)=0<BR>\n" );
document.write( "t=(1/2)(4+/- sqrt (16+60)); sqrt (76)=8.72<BR>\n" );
document.write( "=6.36 seconds<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28300%2C300%2C-10%2C10%2C-25%2C100%2C50%2C-5x%5E2%2B20x%2B75%29 ALIGN=MIDDLE  ALT=\"graph%28300%2C300%2C-10%2C10%2C-25%2C100%2C50%2C-5x%5E2%2B20x%2B75%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );