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CGP EDU Academic Team
Published on: August 13, 2026
If second, third and fourth terms in the expansion of (x + a) n are 240, 720 and 1080 respectively, then n is equal to
Text Solution
Verified by ExpertsThe correct answer is:
5
(5)
T 2 = n C 1 (x) n–1 . a = 240 .......(i)
T 3 = n C 2 (x) n–2 a 2 = 720 .......(ii)
T 4 = n C 3 (x) n–3 a 3 = 1080 .......(iii)
From (i) and (ii)
Here 
= 
= 
= 
⇒ 6x = (n – 1)a
From (ii) and (iii)
9x = 2(n – 2) a
On dividing 
= 
⇒ 3n – 3 = 4n – 8 ⇒ n = 5
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