Question 934984
Let {{{ n }}} = the actual number of
oranges he bought
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The cost of each orange he bought
was {{{ 36/n }}}
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They are asking you " what if each
orange had cost {{{ 36/n - .5 }}}?
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Now you can say:
{{{ 36 = ( 36/n - .5 )*( n + 6 ) }}}
{{{ 36 = 36 - .5n + 216/n - 3 }}}
{{{ -.5n + 216/n- 3 = 0 }}}
Multiply both sides by {{{ n }}}
{{{ -.5n^2 - 3n + 216 = 0 }}}
Multiply both sides by {{{ 10 }}}
{{{ -5n^2 - 30n + 2160 = 0 }}}
{{{ -n^2 - 6n + 432 = 0 }}}
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Use the quadratic formula:
{{{ n = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
{{{ a = -1 }}}
{{{ b = -6 }}}
{{{ c = 432 }}}
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{{{ n = (-(-6) +- sqrt( (-6)^2-4*(-1)*432 ))/(2*(-1)) }}}
{{{ n = ( 6 +- sqrt( 36 + 1728 )/(-2)) }}}
{{{ n = ( 6 +- sqrt( 1764 )/(-2)) }}}
{{{ n = ( 6 -  42 ) / (-2) }}}
( use the minus square root to make {{{ n }}} positive )
{{{ n = 36/2 }}}
{{{ n = 18 }}}
Juma bought 18 oranges originally
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check:
{{{ 36 = ( 36/n - .5 )*( n + 6 ) }}}
{{{ 36 = ( 36/18 - .5 )*( 18 + 6 ) }}} 
{{{ 36 = ( 2 - .5 )*24 }}}
{{{ 36 = 1.5*24 }}}
{{{ 36 = 36 }}}
OK
Here's the plot of {{{ f(n) = -n^2 - 6n + 432 }}} 
to locate the roots
{{{ graph( 400, 400, -26, 26, -20, 500, -x^2 - 6x + 432 ) }}}
Looks like a root at {{{ n=18 }}}