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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
-6.31 = 200*((7.05-x)/x) // - 200*((7.05-x)/x)
-(200*((7.05-x)/x))-6.31 = 0
-200*x^-1*(7.05-x)-6.31 = 0
-200*x^-1*(7.05-x)-6.31 = 0
193.69-1410*x^-1 = 0
193.69-1410*x^-1 = 0
-1410*x^-1 = -193.69 // : -1410
x^-1 = 0.13736879
-1 < 0
1/(x^1) = 0.13736879 // * x^1
1 = 0.13736879*x^1 // : 0.13736879
7.27967393 = x^1
x = 7.27967393
x = 7.27967393
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