vă rog dau coroana și 60 puncte
ex2

a)
f(x)>0 ⇔x ∈ {-∞,1)∪(3,+∞)
f(x)≥0 ⇔x ∈ {-∞,1]∪[3,+∞)
f(x)<0 ⇔x ∈ (1,3)
f(x)≤0 ⇔x ∈ [1,3]
b)
f(x)>0 ⇔x ∈ {∅}
f(x)≥0 ⇔x ∈ {∅}
f(x)<0 ⇔x ∈ R
f(x)≤0 ⇔x ∈ R
c)
f(x)>0 ⇔x ∈ R\{2}
f(x)≥0 ⇔x ∈ R
f(x)<0 ⇔x ∈{∅}
f(x)≤0 ⇔x ∈ {2}
d)
f(x)>0 ⇔x ∈ (-1,2)
f(x)≥0 ⇔x ∈ [-1,2]
f(x)<0 ⇔x ∈ {-∞,-1)∪(2,+∞)
f(x)≤0 ⇔x ∈ {-∞,-1]∪[2,+∞)