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AP EAMCET · Maths · Binomial Theorem

If the coefficients of \(x^{10}\) and \(x^{11}\) in the expansion of \(\left(1+\alpha x+\beta x^2\right)(1+x)^{11}\) are 396 and 144 respectively, then \(\alpha^2+\beta^2=\)

  1. A \(10\)
  2. B \(13\)
  3. C \(25\)
  4. D \(20\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(13\)

Step-by-step Solution

Detailed explanation

\(C(x^{10}): \binom{11}{10} + \alpha\binom{11}{9} + \beta\binom{11}{8} = 396\) \(11 + 55\alpha + 165\beta = 396\) \(\alpha + 5\alpha + 15\beta = 36 \implies \alpha + 3\beta = 7 \quad (1)\) \(C(x^{11}): \binom{11}{11} + \alpha\binom{11}{10} + \beta\binom{11}{9} = 144\)…