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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)
(9*x)/(x^2-16)-(8/(x+4)) = 0
(9*x)/(x^2-16)-8*(x+4)^-1 = 0
(9*x)/(x^2-16)-8/(x+4) = 0
(9*x*(x+4))/((x^2-16)*(x+4))+(-8*(x^2-16))/((x^2-16)*(x+4)) = 0
9*x*(x+4)-8*(x^2-16) = 0
x^2+36*x+128 = 0
x^2+36*x+128 = 0
x^2+36*x+128 = 0
DELTA = 36^2-(1*4*128)
DELTA = 784
DELTA > 0
x = (784^(1/2)-36)/(1*2) or x = (-784^(1/2)-36)/(1*2)
x = -4 or x = -32
(x+32)*(x+4) = 0
((x+32)*(x+4))/((x^2-16)*(x+4)) = 0
((x+32)*(x+4))/((x^2-16)*(x+4)) = 0 // * (x^2-16)*(x+4)
(x+32)*(x+4) = 0
( x+32 )
x+32 = 0 // - 32
x = -32
( x+4 )
x+4 = 0 // - 4
x = -4
x in { -4}
x = -32
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