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D( x )
3-x = 0
x-3 = 0
3-x = 0
3-x = 0
3-x = 0 // - 3
-x = -3 // * -1
x = 3
x-3 = 0
x-3 = 0
x-3 = 0 // + 3
x = 3
x in (-oo:3) U (3:+oo)
(6*x-3)/(3-x)+15/(x-3) = 0
((6*x-3)*(x-3))/((3-x)*(x-3))+(15*(3-x))/((3-x)*(x-3)) = 0
(6*x-3)*(x-3)+15*(3-x) = 0
6*x^2-36*x+54 = 0
6*x^2-36*x+54 = 0
6*(x^2-6*x+9) = 0
x^2-6*x+9 = 0
DELTA = (-6)^2-(1*4*9)
DELTA = 0
x = 6/(1*2)
x = 3 or x = 3
6*(x-3)^2 = 0
(6*(x-3)^2)/((3-x)*(x-3)) = 0
(6*(x-3)^2)/((3-x)*(x-3)) = 0 // * (3-x)*(x-3)
6*(x-3)^2 = 0
x-3 = 0 // + 3
x = 3
x in { 3}
x belongs to the empty set
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