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D( x )
x+4 = 0
x^2-16 = 0
x+4 = 0
x+4 = 0
x+4 = 0 // - 4
x = -4
x^2-16 = 0
x^2-16 = 0
1*x^2 = 16 // : 1
x^2 = 16
x^2 = 16 // ^ 1/2
abs(x) = 4
x = 4 or x = -4
x in (-oo:-4) U (-4:4) U (4:+oo)
x/(x^2-16) = 4/(x^2-16)-(2/(x+4)) // - 4/(x^2-16)-(2/(x+4))
x/(x^2-16)-(4/(x^2-16))+2/(x+4) = 0
x/(x^2-16)-4*(x^2-16)^-1+2/(x+4) = 0
x/(x^2-16)-4/(x^2-16)+2/(x+4) = 0
(x*(x+4))/((x^2-16)*(x+4))+(-4*(x+4))/((x^2-16)*(x+4))+(2*(x^2-16))/((x^2-16)*(x+4)) = 0
x*(x+4)-4*(x+4)+2*(x^2-16) = 0
x^2+2*x^2-32-16 = 0
3*x^2-48 = 0
(3*x^2-48)/((x^2-16)*(x+4)) = 0
(3*x^2-48)/((x^2-16)*(x+4)) = 0 // * (x^2-16)*(x+4)
3*x^2-48 = 0
3*x^2 = 48 // : 3
x^2 = 16
x^2 = 16 // ^ 1/2
abs(x) = 4
x = 4 or x = -4
x in { 4}
x in { -4}
x belongs to the empty set
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