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D( x )
(7*39*x)/13 = 0
(7*39*x)/13 = 0
(7*39*x)/13 = 0
21*x = 0 // : 21
x = 0
x in (-oo:0) U (0:+oo)
(3*(7*x-((37*x)/72)))/((7*39*x)/13) = 89 // - 89
(3*(7*x-((37*x)/72)))/((7*39*x)/13)-89 = 0
(3*(7*x+(-37/72)*x))/((7*39*x)/13)-89 = 0
(3*467/72*x)/(21*x)-89 = 0
(3*467/72*x)/(21*x)+(-89*21*x)/(21*x) = 0
3*467/72*x-89*21*x = 0
-44389/24*x = 0
(-44389/24*x)/(21*x) = 0
(-44389/24*x)/(21*x) = 0 // * 21*x
(-44389*x)/24 = 0
-44389/24*x = 0 // : -44389/24
x = 0
x in { 0}
x belongs to the empty set
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