document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=785319>Question 785319</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The following table shows worldwide sales of a certain type of cell phone and their average wholesale prices in 2009 and 2010.<BR>\n" );
document.write( "Quarter  	    Q1 2009     	    Q1 2010    <BR>\n" );
document.write( "Wholesale Price ($) 	163 	              153<BR>\n" );
document.write( "Sales (millions) 	175 	              214<BR>\n" );
document.write( "(a) Use the data to obtain a linear demand function for cell phones.<BR>\n" );
document.write( "q(p) = 	\r<BR>\n" );
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document.write( "Use your demand equation to predict sales to the nearest million phones if the price was set at $156. (Round your answer to the nearest million phones.)\r<BR>\n" );
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document.write( "(b) Fill in the blank.<BR>\n" );
document.write( "For every $1 increase in price, sales of cell phones decrease by<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #477459 by </B><A HREF=/tutors/aboutme.mpl?userid=xinxin><B>xinxin(76)</B></A><img src=\"/images/stars/stars-08.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=xinxin><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=477459\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a)Let the function be Q(P)=aP+b, then <BR>\n" );
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document.write( " <TR><TD  ALIGN=MIDDLE>Solved by <A  rel=nofollow HREF=http://wiki.algebra.com/index.php/Tutoring_-_pluggable_solvers>pluggable</A> solver: <A  rel=nofollow HREF=linear.solver>Linear System solver (using determinant)</A></TD></TR>\n" );
document.write( "<TR><TD  ALIGN=LEFT>Solve:<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+system%28+%0D%0A++++163%5Ca+%2B+1%5Cb+=+175%2C%0D%0A++++153%5Ca+%2B+1%5Cb+=+214+%29%0D%0A++ ALIGN=MIDDLE  ALT=\"+system%28+%0D%0A++++163%5Ca+%2B+1%5Cb+=+175%2C%0D%0A++++153%5Ca+%2B+1%5Cb+=+214+%29%0D%0A++\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  <BR>\n" );
document.write( "  Any system of equations:<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+system%28+%0D%0A++++a%5B11%5D%2Aa+%2B+a%5B12%5D%2Ab+=+b%5B1%5D%2C%0D%0A++++a%5B21%5D%2Aa+%2B+a%5B22%5D%2Ab+=+b%5B2%5D%29%0D%0A++ ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  <BR>\n" );
document.write( "  has solution<BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+system%28+%0D%0A++++a+=+%28b%5B1%5D%2Aa%5B22%5D+-+b%5B2%5D%2Aa%5B12%5D%29%2F%28a%5B11%5D%2Aa%5B22%5D-a%5B21%5D%2Aa%5B12%5D%29%2C%0D%0A++++b+=+%28a%5B11%5D%2Ab%5B2%5D+-+a%5B21%5D%2Ab%5B1%5D%29%2F%28a%5B11%5D%2Aa%5B22%5D-a%5B21%5D%2Aa%5B12%5D%29%0D%0A++++%29%0D%0A++ ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  or<BR>\n" );
document.write( "  <BR>\n" );
document.write( "  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+system%28+%0D%0A++++++a+=+%28175%2A1+-+214%2A1%29%2F%28163%2A1-153%2A1%29+=+-3.9%2C%0D%0A++++++b+=+%28163%2A214+-+153%2A175%29%2F%28163%2A1-153%2A1%29+=+810.7%0D%0A++++%29%0D%0A++ ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "  <BR>\n" );
document.write( "  (a=-3.9, b=810.7}<BR>\n" );
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document.write( "Q(P)=-3.9P+810.7<BR>\n" );
document.write( "When P=156, Q(P)=202.3=202 millions\r<BR>\n" );
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document.write( "b)-3.9P+810.7-(-3.9*(P+1)+810.7)=3.9 millions=3900000<BR>\n" );
document.write( ".....sales of cell phones decrease by 3900000.<BR>\n" );
document.write( " </SPAN>\n" );
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