1.

Find the coefficient of \(x^n\) in the expansion of \((1+x)(1-x)^n\)

Answer»

We have, 

Coefficient of \(x^n\) in \((1+x)(1-x)^n\)

= coefficient of \(x^n\) in \((1-x)^n\) + coefficient of \(x^{n-1}\) in \((1-x)^n\)

\((-1)^n\) nCn+(-1)n-1nCn-1

=\((-1)^n(1-n)\)



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