document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=35039>Question 35039</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The number of people n in the mall is modeled by the formula: n=-100x(sq)+1200x where x is the number of hours since the mall oopened this morning.  If the mall opened at 9 am, when were there 2000 or more people in the mall? </SPAN>\n" );
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document.write( "# of people = -100x^2 + 1200x\r<BR>\n" );
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document.write( "for 2000 people to be there,\r<BR>\n" );
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document.write( "2000 = 100x^2 + 1200x\r<BR>\n" );
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document.write( "re-arranging,\r<BR>\n" );
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document.write( "-100x^2 + 1200x = 2000\r<BR>\n" );
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document.write( "i.e. -x^2 + 12x = 20\r<BR>\n" );
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document.write( "-x^2 +12x -20 = 0<BR>\n" );
document.write( "-x^2 + 10x + 2x - 20 = 0\r<BR>\n" );
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document.write( "solve, you get x = 2hrs </SPAN>\n" );
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