1.

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)

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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