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In the expansion of $\left(x-\frac{1}{x}\right)^6$, the constant term is
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$-20$
In the expansion of $\left(x-\frac{1}{x}\right)^6$
the general term is ${ }^6 C_r x^{6-r}\left(-\frac{1}{x}\right)^r={ }^6 C_r(-1)^r x^{6-2 r}$
For term independent of $x, 6-2 r=0 \Rightarrow r=3$
Thus the required coefficient $=(-1)^3 \cdot{ }^6 C_3=-20$
the general term is ${ }^6 C_r x^{6-r}\left(-\frac{1}{x}\right)^r={ }^6 C_r(-1)^r x^{6-2 r}$
For term independent of $x, 6-2 r=0 \Rightarrow r=3$
Thus the required coefficient $=(-1)^3 \cdot{ }^6 C_3=-20$
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