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D( x )
(4-x)/0.1 = 0
(4-x)/0.1 = 0
(4-x)/0.1 = 0
4-x = 0 // - 4
-x = -4 // * -1
x = 4
x in (-oo:4) U (4:+oo)
2 = (x/0.05)/((4-x)/0.1) // - (x/0.05)/((4-x)/0.1)
2-((x/0.05)/((4-x)/0.1)) = 0
2-2*x*(4-x)^-1 = 0
(-2*x)/(4-x)+2 = 0
(-2*x)/(4-x)+(2*(4-x))/(4-x) = 0
2*(4-x)-2*x = 0
8-4*x = 0
(8-4*x)/(4-x) = 0
(8-4*x)/(4-x) = 0 // * 4-x
8-4*x = 0
8-4*x = 0 // - 8
-4*x = -8 // : -4
x = -8/(-4)
x = 2
x = 2
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