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AP EAMCET · Maths · Binomial Theorem

The coefficient of \(x^5\) in the expansio of \((1+x)^{21}+(1+x)^{22}+\ldots+(1+x)^{30}\) is

  1. A \({ }^{31} \mathrm{C}_6-{ }^{21} \mathrm{C}_6\)
  2. B \({ }^{51} C_5\)
  3. C \({ }^9 \mathrm{C}_5\)
  4. D \({ }^{30} \mathrm{C}_5+{ }^{20} \mathrm{C}_5\)
Verified Solution

Answer & Solution

Correct Answer

(A) \({ }^{31} \mathrm{C}_6-{ }^{21} \mathrm{C}_6\)

Step-by-step Solution

Detailed explanation

As we know, coefficient of \(x^r\) in the binomial expansion of \((1+x)^n\) is given by \({ }^n C_r\). So, coefficient of \(x^5\) in the binomial expansion of…