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NCERT Class XI Mathematics - Relations and Functions - Solutions
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Question : 24 of 36
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Find the range of each of the following functions. (i) f (x) = 2 – 3x, x ∈ R, x > 0. (ii) f (x) = + 2, x is a real number. (iii) f (x) = x, x is a real number.
Solution:
(i) Given f (x) = 2 – 3x, x ∈ R, x > 0 Since x > 0 ⇒ –3x < 0 ⇒ 2 – 3x < 2 + 0 ⇒ f(x) < 2 ∴ The range of f (x) is (– ∞, 2). (ii) Given f (x) = + 2, x is a real number We know ≥ 0 ⇒ x2 + 2 ≥ 0 + 2 ⇒ + 2 ≥ 2 ⇒ f (x) ≥ 2 ∴ The range of f (x) is [2, ∞). (iii) Given f (x) = x, x is a real number. Let y = f (x) = x ⇒ y = x ∴ Range of f (x) = Domain of f (x) ∴ Range of f (x) is R.
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