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D( x )
x = 0
5*x = 0
x = 0
x = 0
5*x = 0
5*x = 0
5*x = 0 // : 5
x = 0
x in (-oo:0) U (0:+oo)
23/(5*x) = 4/x // - 4/x
23/(5*x)-(4/x) = 0
23/(5*x)-4*x^-1 = 0
3/5*x^-1 = 0 // : 3/5
x^-1 = 0
x należy do O
x belongs to the empty set