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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
2*x+5 = 12/x // - 12/x
2*x-(12/x)+5 = 0
2*x-12*x^-1+5 = 0
2*x^1-12*x^-1+5*x^0 = 0
(2*x^2+5*x^1-12*x^0)/(x^1) = 0 // * x^2
x^1*(2*x^2+5*x^1-12*x^0) = 0
x^1
2*x^2+5*x-12 = 0
2*x^2+5*x-12 = 0
DELTA = 5^2-(-12*2*4)
DELTA = 121
DELTA > 0
x = (121^(1/2)-5)/(2*2) or x = (-121^(1/2)-5)/(2*2)
x = 3/2 or x = -4
x in { -4, 3/2}
x in { -4, 3/2 }
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