7.Binomial Theorem
hard

If $\alpha$ and $\beta$ be the coefficients of $x^{4}$ and $x^{2}$ respectively in the expansion of

$(\mathrm{x}+\sqrt{\mathrm{x}^{2}-1})^{6}+(\mathrm{x}-\sqrt{\mathrm{x}^{2}-1})^{6}$, then 

A

$\alpha+\beta=60$

B

$\alpha+\beta=30$

C

$\alpha-\beta=-132$

D

$\alpha-\beta=60$

(JEE MAIN-2020)

Solution

$2\left[^{6} \mathrm{C}_{0} \mathrm{x}^{6}+^{6} \mathrm{C}_{2} \mathrm{x}^{4}\left(\mathrm{x}^{2}-1\right)+6 \mathrm{C}_{4} \mathrm{x}^{2}\left(\mathrm{x}^{2}-1\right)^{2}+^{6} \mathrm{C}_{6}\left(\mathrm{x}^{2}-1\right)^{3}\right]$

$\alpha=-96 \;and\; \beta=36$

$\therefore \alpha-\beta=-132$

Standard 11
Mathematics

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