−8≤f(x)≤−5-8 \leq f(x) \leq-5−8≤f(x)≤−5
f(x)>0f(x)>0f(x)>0
−5≤f(x)≤4-5 \leq f(x) \leq 4−5≤f(x)≤4
−6≤f(x)≤0-6 \leq f(x) \leq 0−6≤f(x)≤0