document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=544742>Question 544742</A>: <I><SPAN STYLE=\"word-break: break-all;\"> the amount of cloth used to amke four cutains is given by the function A=-4xsquared+40x, where x ia the width of one cutain in feet ad A i sthe total area in square feet. Find the width that maximizes the area of the curtains. What is the maximum area? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #355207 by </B><A HREF=/tutors/aboutme.mpl?userid=lwsshak3><B>lwsshak3(11628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=lwsshak3><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=355207\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the amount of cloth used to amke four cutains is given by the function A=-4xsquared+40x, where x ia the width of one cutain in feet ad A i sthe total area in square feet. Find the width that maximizes the area of the curtains. What is the maximum area?<BR>\n" );
document.write( "**<BR>\n" );
document.write( "Standard form of equation for parabola that opens downward (parabola has a maximum): <BR>\n" );
document.write( "y=-A(x-h)^2+k, (h,k)=(x,y) coordinates of vertex.<BR>\n" );
document.write( "..<BR>\n" );
document.write( "A=-4x^2+40x<BR>\n" );
document.write( "complete the square<BR>\n" );
document.write( "A=-4(x^2-10x+25)+100<BR>\n" );
document.write( "A=-4(x-5)^2+100<BR>\n" );
document.write( "Vertex:(5,100)<BR>\n" );
document.write( "ans:<BR>\n" );
document.write( "width=5 ft<BR>\n" );
document.write( "maximum area=100 sq ft </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );