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The ratio of the fifth term from the beginning to the fifth term from the end in the expansion of 2 4 + 1 3 4 n is 6 : 1 . If n = 20 λ , then the value of λ is

Correct answer

2

Step-by-step solution

T 5 T n − 5 + 2 = n C 4 2 1 4 n − 4 ⋅ 3 − 1 4 4 n C n − 4 2 1 4 4 ⋅ 3 − 1 4 n − 4 T 5 T n − 5 + 2 = 2 n − 4 4 ⋅ 3 n − 4 4 6 = 6 ⇒ 6 n − 4 4 = 6 3 2 ⇒ n = 10 = 20 λ ⇒ λ = 2

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