1.

Show that the term independent of x in the expansion of `(x-1/x)^(10) is -252`.

Answer» `T_(r+1)=(-1)^(r)*^(10) C_(r)x^((10-1))*(1/x)^(r) = (-1)^(r)*^(10)C_(r)x^((10-20)).`
`Putting 10-2r =0, " we get " r=5.`
` :. (T_(6) -1)^(5) *^(10)C _(5)= - ( 10 xx 9 xx 8 xx 7 xx 6 )/(5 xx 4 xx 3 xx 2 xx 1 ) = - 252.`


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