document.write( "Question 518396: \"A charter flight club charges its members $400 per year. But, for each new member in excess of 60, the charge for every member is reduced by $5. What number of members leads to a maximum revenue?\" \n" ); document.write( "
Algebra.Com's Answer #345196 by ankor@dixie-net.com(22740)\"\" \"About 
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\"A charter flight club charges its members $400 per year.
\n" ); document.write( " But, for each new member in excess of 60, the charge for every member is reduced by $5.
\n" ); document.write( " What number of members leads to a maximum revenue?\"
\n" ); document.write( ":
\n" ); document.write( "Let x = no. of $5 decrease for each member
\n" ); document.write( "and
\n" ); document.write( "Let x = increase in membership
\n" ); document.write( ":
\n" ); document.write( "f(x) = (400-5x)(60+x)
\n" ); document.write( "FOIL
\n" ); document.write( "f(x) = 24000 + 400x - 300x - 5x^2
\n" ); document.write( "A quadratic equation
\n" ); document.write( "f(x) = -5x^2 + 100x + 24000
\n" ); document.write( "Max revenue will occur at the axis to symmetry, x = -b/(2a)
\n" ); document.write( "a = -5, b = 100
\n" ); document.write( "x = \"%28-100%29%2F%282%2A-5%29\"
\n" ); document.write( "x = +10
\n" ); document.write( "A decrease of 5(10) = $50 giving us $350 per member
\n" ); document.write( "An increase of 10 people giving us 70 members for max revenue \n" ); document.write( "
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