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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
x-(45/x) < -4 // + 4
x-(45/x)+4 < 0
x-45*x^-1+4 < 0
x-45*x^-1+4 = 0
1*x^1-45*x^-1+4*x^0 = 0
(1*x^2+4*x^1-45*x^0)/(x^1) = 0 // * x^2
x^1*(1*x^2+4*x^1-45*x^0) = 0
x^1
x^2+4*x-45 = 0
x^2+4*x-45 = 0
DELTA = 4^2-(-45*1*4)
DELTA = 196
DELTA > 0
x = (196^(1/2)-4)/(1*2) or x = (-196^(1/2)-4)/(1*2)
x = 5 or x = -9
x in { -9, 5}
(x+9)*(x-5) < 0
(-oo:-9) (-9:5) (5:+oo) x+9 - + + x-5 - - +
x in (-9:0) U (0:5)
(-9:0) U (0:5)
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