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D( x )
x^2-16 = 0
x+4 = 0
x-4 = 0
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+4 = 0
x+4 = 0
x+4 = 0 // - 4
x = -4
x-4 = 0
x-4 = 0
x-4 = 0 // + 4
x = 4
x in (-oo:-4) U (-4:4) U (4:+oo)
x/(x+4)-(4/(x-4)) = (x^2+16)/(x^2-16) // - (x^2+16)/(x^2-16)
x/(x+4)-(4/(x-4))-((x^2+16)/(x^2-16)) = 0
x/(x+4)-4*(x-4)^-1-((x^2+16)/(x^2-16)) = 0
x/(x+4)-4/(x-4)+(-1*(x^2+16))/(x^2-16) = 0
(x*(x-4)*(x^2-16))/((x+4)*(x-4)*(x^2-16))+(-4*(x+4)*(x^2-16))/((x+4)*(x-4)*(x^2-16))+(-1*(x^2+16)*(x+4)*(x-4))/((x+4)*(x-4)*(x^2-16)) = 0
x*(x-4)*(x^2-16)-4*(x+4)*(x^2-16)-1*(x^2+16)*(x+4)*(x-4) = 0
x^4-x^4-8*x^3-32*x^2+128*x+256+256 = 0
128*x-8*x^3-32*x^2+512 = 0
128*x-8*x^3-32*x^2+512 = 0
8*(16*x-x^3-4*x^2+64) = 0
16*x-x^3-4*x^2+64
x*(16-x^2)-4*x^2+64
4*(16-x^2)+x*(16-x^2)
(x+4)*(16-x^2)
8*(x+4)*(16-x^2) = 0
(8*(x+4)*(16-x^2))/((x+4)*(x-4)*(x^2-16)) = 0
(8*(x+4)*(16-x^2))/((x+4)*(x-4)*(x^2-16)) = 0 // * (x+4)*(x-4)*(x^2-16)
8*(x+4)*(16-x^2) = 0
( 16-x^2 )
-1*x^2 = -16 // : -1
x^2 = 16
x^2 = 16 // ^ 1/2
abs(x) = 4
x = 4 or x = -4
( x+4 )
x+4 = 0 // - 4
x = -4
x in { 4}
x in { -4}
x belongs to the empty set
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