document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=886052>Question 886052</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Minimum Cost: A rectangular area adjacent to a river is to be fenced in; no fence is needed on the river side. The enclosed area is to be 1,000 square feet. Fencing for the side parallel to the river is $5 per linear foot, and fencing for the other two sides is $8 per linear foot; the four corner posts are $25 apiece. Let x be the length of one of the sides perpendicular to the river. <BR>\n" );
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document.write( "a)      Write a function C(x) that describes the cost of the project.<BR>\n" );
document.write( "b)      What is the domain of C?\r<BR>\n" );
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document.write( " I don't know exactly how to do this. Any suggestions on what I mess up on is greatly appreciated. \r<BR>\n" );
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document.write( " 4 * 25 = 100 NOT A VARIABLE COST\r<BR>\n" );
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document.write( " 5y * 8x = 1,000       I put it like this because it is a rectangle and I was trying to get the area. So I multiplied l * w. \r<BR>\n" );
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document.write( "5y * 8x - 5y = 1,000 - 5y<BR>\n" );
document.write( "8x = -5y + 1,000<BR>\n" );
document.write( "8x - 1,000 = -5y + 1,000 - 1,000<BR>\n" );
document.write( "8x - 1,000 = -5y<BR>\n" );
document.write( "8x - 1,000 / -5 = -5y / -5<BR>\n" );
document.write( "-8/5x - 200 <BR>\n" );
document.write( "C(x) = - 8/5x - 200\r<BR>\n" );
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document.write( "I was told it was wrong. I've also tried the following. \r<BR>\n" );
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document.write( "8x^2 + 5 y + 100 = 1000<BR>\n" );
document.write( "8x^2 5y + 100 - 100 = 1000 - 100<BR>\n" );
document.write( "8x^2 + 5y = 900<BR>\n" );
document.write( "8x^2 + 5y - 8x^2 = -8x^2 + 900<BR>\n" );
document.write( "5y = -8x^2 + 900<BR>\n" );
document.write( "5y / 5 = -8x2 + 900 / 5<BR>\n" );
document.write( "y = -8/5x^2 +180\r<BR>\n" );
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document.write( "8x + 8x + 5y + 100 = 1000<BR>\n" );
document.write( "16x + 5y + 100 = 1000<BR>\n" );
document.write( "16x + 5y + 100 - 100 = 1000 - 100 <BR>\n" );
document.write( "16x + 5y = 900<BR>\n" );
document.write( "16x + 5y - 16x = -16x + 900<BR>\n" );
document.write( "5y = -16x + 900<BR>\n" );
document.write( "5y / 5 = -16x + 900 / 5<BR>\n" );
document.write( "y = -16/5x + 180\r<BR>\n" );
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document.write( "I'm not sure how to explain the cost of the project or to find the domain either. \r<BR>\n" );
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document.write( "Thank you in advance. Chastity Moore </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #535648 by </B><A HREF=/tutors/aboutme.mpl?userid=richwmiller><B>richwmiller(17219)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=richwmiller><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=richwmiller><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=535648\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> x*y=1000<BR>\n" );
document.write( "y=1000/x\r<BR>\n" );
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document.write( "5y+16x+100=C(x)<BR>\n" );
document.write( "5(1000/x)+16x+100=C(x)\r<BR>\n" );
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document.write( "The domain is all positive real numbers.<BR>\n" );
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