document.write( "Question 79036: The profit on a watch is given by P = x2 – 13x – 80, where x is the number of watches sold per day. How many watches were sold on a day when there was a $50 loss? \n" ); document.write( "

Algebra.Com's Answer #56699 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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The profit on a watch is given by P = x^Ch2 – 13x – 80, where x is the number of watches sold per day. How many watches were sold on a day when there was a $50 loss?
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\n" ); document.write( "x^2 - 13x - 80 = -50; negative because of a loss of 50
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\n" ); document.write( "x^2 - 13x - 80 + 50 = 0; add 50 to both sides
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\n" ); document.write( "x^2 - 13x - 30 = 0
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\n" ); document.write( "Easily factors to:
\n" ); document.write( "(x-15) (x+2) = 0
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\n" ); document.write( "x = -2
\n" ); document.write( "and
\n" ); document.write( "x = +15 watches sold for a loss of $50
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\n" ); document.write( "Check; substitute 15 for x in the original equation:
\n" ); document.write( "15^2 - 13(15) - 80 =
\n" ); document.write( "225 - 195 - 80 = -50
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