- #1
twoski
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Homework Statement
If A and B are sets and f : A → B, then for any subset S of A we define:
f(S) = {b ∈ B : b = f(a) for some a ∈ S}
Similarly, for any subset T of B we define the pre-image of T as:
f[itex]^{-1}[/itex](T) = {a ∈ A : f(a) ∈ T}
Note that f[itex]^{-1}[/itex](T) is well defined even if f does not have an inverse.
Now let f : R → R be defined as f(x) = [itex]x^{2}[/itex]
Let S1 denote the closed interval [−2, 1], and let S2 be the open interval (−1, 2). Also let T1 = S1 and T2 = S2.
Determine:
f(S1 ∪ S2)
f(S1) ∪ f(S2)
f(S1 ∩ S2)
f(S1) ∩ f(S2)
f[itex]^{-1}[/itex](T1 ∪ T2)
f[itex]^{-1}[/itex](T1) ∪ f[itex]^{-1}[/itex](T2)
f[itex]^{-1}[/itex](T1 ∩ T2)
f[itex]^{-1}[/itex](T1) ∩ f[itex]^{-1}[/itex](T2)
The Attempt at a Solution
I think I'm being asked to verify that each subset satisfies "some b = f(a) for some a ∈ S" where S is the subset i have to compute.
For example, the first question is f(S1 U S2) = f( [-2,2) ).
My question is, what do i have to do next? I can't plug in every value x where -2 =< x < 2 since I'm using real numbers.
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