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D( x )
4-(9*x^2) = 0
4-(9*x^2) = 0
4-(9*x^2) = 0
4-9*x^2 = 0
-9*x^2 = -4 // : -9
x^2 = 4/9
x^2 = 4/9 // ^ 1/2
abs(x) = 2/3
x = 2/3 or x = -2/3
x in (-oo:-2/3) U (-2/3:2/3) U (2/3:+oo)
(6*x-5)/(4-(9*x^2)) = 0
(6*x-5)/(4-9*x^2) = 0
6*x-5 = 0 // + 5
6*x = 5 // : 6
x = 5/6
x = 5/6
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