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D( x )
100-x = 0
100-x = 0
100-x = 0
100-x = 0 // - 100
-x = -100 // * -1
x = 100
x in (-oo:100) U (100:+oo)
50000 = (25000*x)/(100-x) // - (25000*x)/(100-x)
50000-((25000*x)/(100-x)) = 0
50000-25000*x*(100-x)^-1 = 0
(-25000*x)/(100-x)+50000 = 0
(-25000*x)/(100-x)+(50000*(100-x))/(100-x) = 0
50000*(100-x)-25000*x = 0
5000000-75000*x = 0
(5000000-75000*x)/(100-x) = 0
(5000000-75000*x)/(100-x) = 0 // * 100-x
5000000-75000*x = 0
5000000-75000*x = 0 // - 5000000
-75000*x = -5000000 // : -75000
x = -5000000/(-75000)
x = 200/3
x = 200/3
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