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If |x + 2| ≤ 9, then A.x ∈ (–7, 11) B. x ∈ [–11, 7] C. x ∈ (∞, –7) ∪ (11, ∞) D. x ∈ (–∞, –7) ∪ [11, ∞) |
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Answer» B. x ∈ [-11, 7] Given, |x + 2| ≤ 9 There are two cases, (x + 2) ≤ 9 ⇒ x ≤ 7 ⇒ x ∈ (-∞,7] [1] And -(x + 2) ≤ 9 ⇒ -x – 2 ≤ 9 ⇒ -x ≤ 11 ⇒ x ≥ -11 [Multiplication by negative inverts the inequality sign] ⇒ x ∈ [-11, ∞) [2] From [1] and [2], we get ⇒ x ∈ [-11, 7] |
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