document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=64972>Question 64972</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I have tried and tried to remember the formulas and have done research to refresh my memory, but it's just not working.  Here's the question:\r<BR>\n" );
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document.write( "If you charge $1 per cup of a drink and sell 50 cups, then you raise your price to $2 per cup and sell only 25 cups, write an equation for the number of cups that you sell as a function of the price you charge.  \"C\" is for # of cups and \"P\" is for the price you charge.  Assume that the function is linear. \r<BR>\n" );
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document.write( "Thank you\r<BR>\n" );
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document.write( "This problem is from an assignment from a course through correspondence. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #45476 by </B><A HREF=/tutors/aboutme.mpl?userid=cristiana><B>cristiana(10)</B></A><img src=\"/images/stars/stars-05.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=cristiana><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=45476\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> All right, so the start point is that our function is linear. <BR>\n" );
document.write( "Draw the coordinate system. <BR>\n" );
document.write( "Let the price be x and number of cups be y.<BR>\n" );
document.write( "We know that when x = 1, y = 50. Plot this point. <BR>\n" );
document.write( "We also know that when x = 2, y = 25. Plot this point too. <BR>\n" );
document.write( "Draw a line between the two plotted points. <BR>\n" );
document.write( "Let's try to find the point-intercept equation of this line. Since all we know is the two points, we can make a system of two point-slope equations and find the slope. Let's do that:<BR>\n" );
document.write( "point (1,50): y-50 = m(x-1); y = m(x-1) + 50<BR>\n" );
document.write( "point (2,25): y-25 = m(x-2); y = m(x-2) + 25<BR>\n" );
document.write( "Therefore, m = -25 <BR>\n" );
document.write( "Substitute -25 for m in any of the above two equations to get:<BR>\n" );
document.write( "y=-25(x-1)+50   <BR>\n" );
document.write( "or<BR>\n" );
document.write( "y=-25(x-2)+25 \r<BR>\n" );
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document.write( "You can now check these equations by replacing x=1 ($1/cup) and x=2 ($2/cup)...<BR>\n" );
document.write( " \r<BR>\n" );
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document.write( "Hope it helped! <BR>\n" );
document.write( "Cristiana </SPAN>\n" );
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