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The set of values of x for which the inequalities x2 – 3x – 10 < 0, 10x – x2 – 16 > 0 hold simultaneously is(a) (–2, 5) (b) (2, 8) (c) (–2, 8) (d) (2, 5) |
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Answer» (d) (2, 5) x2 – 3x – 10 < 0 ⇒ (x + 2) (x – 5) < 0 ⇒ (x – (–2)) (x – 5) < 0 ⇒ x∈ (–2, 5) (If a < b, then (x – a) (x – b) < 0 ⇒ a < x < b) 10x – x2 – 16 > 0 ⇒ x2 – 10x + 16 < 0 ⇒ (x – 2) (x – 8) < 0 ⇒ x∈ (2, 8) (If a < 0, then (x – a) (x – b) < 0 ⇒ a < x < b) ∴ x∈ (–2, 5) ∩ (2, 8) ⇒ x∈ (2, 5). |
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