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o
•N={0,1,2, . . .}
•Z={. . . , −2,−1,0,1,2, . . .}
•Q={p
q, p ∈N, q ∈N∗}
•R
•C
0N∗=
{1,2,3, . . .}
+
R+= [0,+∞[R∗
+=]0,+∞[
R R
Q
R
+∞ −∞
[a, b] = {x∈R|a≤x≤b},[a, b[= {x∈R|a≤x<b},[a, +∞[= {x∈R|a≤x},
]a, b] = {x∈R|a<x≤b},]a, b[= {x∈R|a<x<b},]a, +∞[= {x∈R|a<x},
]− ∞, b] = {x∈R|x≤b},]− ∞, b[= {x∈R|x<b},]− ∞,+∞[= R.