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QJEEM24Ma76c0: JEE Main 2024 Mathematics - Class 11 JEEM24Ma76c0 Solution: In the expansion of , the sum of the coefficients of and is…

In the expansion of (1+x)(1−x2)(1+3x+3x2+1x3)5,x≠0(1+x)\left(1-x^2\right)\left(1+\frac{3}{x}+\frac{3}{x^2}+\frac{1}{x^3}\right)^5, x \neq 0 , the sum of the coefficients of x3x^3 and x−13x^{-13} is equal to __________.

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amp;(1+x)(1−x2)(1+3x+3x2+1x3)5amp;=(1+x)(1−x2)((1+1x)3)5amp;=(1+x)2(1−x)(1+x)15x15amp;=(1+x)17−x(1+x)17x15\begin{aligned}& (1+x)\left(1-x^2\right)\left(1+\frac{3}{x}+\frac{3}{x^2}+\frac{1}{x^3}\right)^5 \\& =(1+x)\left(1-x^2\right)\left(\left(1+\frac{1}{x}\right)^3\right)^5 \\& =\frac{(1+x)^2(1-x)(1+x)^{15}}{x^{15}} \\& =\frac{(1+x)^{17}-x(1+x)^{17}}{x^{15}}\end{aligned}

=coeff⁡(x3)=\operatorname{coeff}\left(\mathrm{x}^3\right) in the expansion ≈coeff⁡(x18)\approx \operatorname{coeff}\left(\mathrm{x}^{18}\right) in

amp;(1+x)17−x(1+x)17amp;=0−1amp;=−1\begin{aligned}& (1+x)^{17}-x(1+x)^{17} \\& =0-1 \\& =-1\end{aligned}

coeff⁡(x−13)\operatorname{coeff}\left(\mathrm{x}^{-13}\right) in the expansion ≈coeff⁡(x2)\approx \operatorname{coeff}\left(\mathrm{x}^2\right) in

amp;(1+x)17−x(1+x)17amp;=(172)−(171)amp;=17×8−17amp;=17×7amp;=119\begin{aligned}& (1+x)^{17}-x(1+x)^{17} \\& =\left(\begin{array}{c}17 \\2\end{array}\right)-\left(\begin{array}{c}17 \\1\end{array}\right) \\& =17 \times 8-17 \\& =17 \times 7 \\& =119\end{aligned}

Hence Answer =119−1=118=119-1=118

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