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Question
If f : Q → Q is defined as f(x) = x2, then f−1 (9) is equal to
Options
(a) 3
(b) −3
(c) {−3, 3}
(d) ϕ
Solution
(c) {−3, 3}
If f : A → B, such that y ∈ B, then
In other words,
Then, f (x) = 9
⇒ x2 = 9
⇒ x = ± 3
∴ \[f^{- 1}\] {9} = {- 3, 3}.
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