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D( x )
x = 0
x^2-9 = 0
x = 0
x = 0
x^2-9 = 0
x^2-9 = 0
1*x^2 = 9 // : 1
x^2 = 9
x^2 = 9 // ^ 1/2
abs(x) = 3
x = 3 or x = -3
x in (-oo:-3) U (-3:0) U (0:3) U (3:+oo)
x/x-4-3 = 18/(x^2-9) // - 18/(x^2-9)
x/x-(18/(x^2-9))-4-3 = 0
x/x-18*(x^2-9)^-1-4-3 = 0
1-18/(x^2-9)-4-3 = 0
(1*(x^2-9))/(x^2-9)-18/(x^2-9)+(-4*(x^2-9))/(x^2-9)+(-3*(x^2-9))/(x^2-9) = 0
1*(x^2-9)-4*(x^2-9)-3*(x^2-9)-18 = 0
x^2-4*x^2-3*x^2-27+27+36 = 0
9-3*x^2-3*x^2+27 = 0
36-6*x^2 = 0
(36-6*x^2)/(x^2-9) = 0
(36-6*x^2)/(x^2-9) = 0 // * x^2-9
36-6*x^2 = 0
-6*x^2 = -36 // : -6
x^2 = 6
x^2 = 6 // ^ 1/2
abs(x) = 6^(1/2)
x = 6^(1/2) or x = -6^(1/2)
x in { 6^(1/2), -6^(1/2) }
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