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D( x )
(x^2-16)/(7*x^2) = 0
7*x^2 = 0
2*x = 0
(x^2-16)/(7*x^2) = 0
(x^2-16)/(7*x^2) = 0
1*x^2 = 16 // : 1
x^2 = 16
x^2 = 16 // ^ 1/2
abs(x) = 4
x = 4 or x = -4
7*x^2 = 0
7*x^2 = 0
7*x^2 = 0 // : 7
x^2 = 0
x = 0
2*x = 0
2*x = 0
2*x = 0 // : 2
x = 0
x in (-oo:-4) U (-4:0) U (0:4) U (4:+oo)
((6*x^2-(24*x))/(2*x))/((x^2-16)/(7*x^2)) = 0
((6*x^2-24*x)/(2*x))/((x^2-16)/(7*x^2)) = 0
(7*x^2*(6*x^2-24*x))/(2*x*(x^2-16)) = 0
6*x^2-24*x = 0
6*x*(x-4) = 0
x-4 = 0 // + 4
x = 4
6*x*(x-4) = 0
(6*7*x*x^2*(x-4))/(2*x*(x^2-16)) = 0
( 6*x )
6*x = 0 // : 6
x = 0
( 7*x^2 )
7*x^2 = 0 // : 7
x^2 = 0
x = 0
( x-4 )
x-4 = 0 // + 4
x = 4
x in { 0}
x in { 4}
x belongs to the empty set
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