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D( x )
x = 0
5*x+18 = 0
x = 0
x = 0
5*x+18 = 0
5*x+18 = 0
5*x+18 = 0 // - 18
5*x = -18 // : 5
x = -18/5
x in (-oo:-18/5) U (-18/5:0) U (0:+oo)
x/(5*x+18) = -3/x // + -3/x
x/(5*x+18)-(-3/x) = 0
x/(5*x+18)+3*x^-1 = 0
x/(5*x+18)+3/x = 0
(x^2)/(x*(5*x+18))+(3*(5*x+18))/(x*(5*x+18)) = 0
3*(5*x+18)+x^2 = 0
x^2+15*x+54 = 0
x^2+15*x+54 = 0
x^2+15*x+54 = 0
DELTA = 15^2-(1*4*54)
DELTA = 9
DELTA > 0
x = (9^(1/2)-15)/(1*2) or x = (-9^(1/2)-15)/(1*2)
x = -6 or x = -9
(x+9)*(x+6) = 0
((x+9)*(x+6))/(x*(5*x+18)) = 0
((x+9)*(x+6))/(x*(5*x+18)) = 0 // * x*(5*x+18)
(x+9)*(x+6) = 0
( x+6 )
x+6 = 0 // - 6
x = -6
( x+9 )
x+9 = 0 // - 9
x = -9
x in { -6, -9 }
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