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D( f )
f = 0
f = 0
f = 0
f in (-oo:0) U (0:+oo)
15/f < 5 // - 5
15/f-5 < 0
15*f^-1 < 5
15*f^-1 < 5 // : 15
f^-1 < 5/15
f^-1 < 1/3
1/(f^1) < 1/3
f <> 0
1/(f^1) < 1/3 // * f^2
(f^2)/(f^1) < 1/3*f^2
f^1 < 1/3*f^2
f-1/3*f^2 < 0
f^1*(1-1/3*f) < 0
f < 0
-(abs(f))^1*(1/3*(abs(f))^1+1) < 0 // : -(abs(f))^1
1/3*(abs(f))^1+1 > 0
1/3*(abs(f))^1 > -1 // : 1/3
(abs(f))^1 > -1/1/3
(abs(f))^1 > -3 // ^ 1/1
abs(f) > (-3)^(1/1)
abs(f) > -3
f in (-oo:0)
f < 0
f > 0
f^1*(1-(1/3*f^1)) < 0 // : f^1
1-(1/3*f^1) < 0
1 < 1/3*f^1 // : 1/3
1/1/3 < f^1 // ^ 1/1
(1/1/3)^(1/1) < f
f in (3:+oo)
f > 0
f in (-oo:0) U (3:+oo)
f in (-oo:0) U (3:+oo)
(-oo:0) U (3:+oo)
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