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D( x )
5*x-15 = 0
4*x^2-36 = 0
5*x-15 = 0
5*x-15 = 0
5*x-15 = 0 // + 15
5*x = 15 // : 5
x = 15/5
x = 3
4*x^2-36 = 0
4*x^2-36 = 0
4*x^2 = 36 // : 4
x^2 = 9
x^2 = 9 // ^ 1/2
abs(x) = 3
x = 3 or x = -3
x in (-oo:-3) U (-3:3) U (3:+oo)
(((x^2-(6*x)+9)/(4*x^2-36))*(4*x+12))/(5*x-15) = 0
(((x^2-6*x+9)/(4*x^2-36))*(4*x+12))/(5*x-15) = 0
((x^2-6*x+9)*(4*x+12))/((4*x^2-36)*(5*x-15)) = 0
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
(x-3)^2 = 0
((x-3)^2*(4*x+12))/((4*x^2-36)*(5*x-15)) = 0
( 4*x+12 )
4*x+12 = 0 // - 12
4*x = -12 // : 4
x = -12/4
x = -3
( x-3 )
x-3 = 0 // + 3
x = 3
x in { -3}
x in { 3}
x belongs to the empty set
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