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D( x )
x+1000 = 0
x+1000 = 0
x+1000 = 0
x+1000 = 0 // - 1000
x = -1000
x in (-oo:-1000) U (-1000:+oo)
((0.75*x)/(x+1000))/0.9 = 0.003 // - 0.003
((0.75*x)/(x+1000))/0.9-0.003 = 0
(0.75*x)/(0.9*(x+1000))-0.003 = 0
(0.75*x)/(0.9*(x+1000))+(-0.003*0.9*(x+1000))/(0.9*(x+1000)) = 0
0.75*x-0.003*0.9*(x+1000) = 0
0.7473*x-2.7 = 0
(0.7473*x-2.7)/(0.9*(x+1000)) = 0
(0.7473*x-2.7)/(0.9*(x+1000)) = 0 // * 0.9*(x+1000)
0.7473*x-2.7 = 0
0.7473*x-2.7 = 0 // + 2.7
0.7473*x = 2.7 // : 0.7473
x = 2.7/0.7473
x = 3.61300682
x = 3.61300682
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