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TS EAMCET · Maths · Binomial Theorem

The numbers \(a_n=6^n-5 n\) for \(n=1,2,3, \ldots\) when divided by 25 leave the remainder

  1. A 9
  2. B 7
  3. C 3
  4. D 1
Verified Solution

Answer & Solution

Correct Answer

(D) 1

Step-by-step Solution

Detailed explanation

Given, \(a_n=6^n-5 n, n=1,2,3, \ldots\) We take; \(6^n=(1+5)^n\) Expand with binomial expansion \(6^n={ }^n C_0+{ }^n C_1 5+{ }^n C_2 5^2+{ }^n C_3 5^3+\ldots\) \(6^n=1+n \cdot 5+{ }^n C_2 25+{ }^n C_3 5^3+\ldots\)…