1.

Prove that there is no term containing `x^(10)` in the expansion of `(x^(2) - 2/x)^(18).`

Answer» The general term in the given expansion is given by
`T _(r+1)= (-1)^(r) xx.^(18)C_(r) xx (x^(2))^((18-r)) xx (2/x)^(r)`
`rArr T_((r+1))=(-1)^(r) xx.^(18)C_(r) xx 2^ (r) xxx^((36-3r))`.
Let `T_(r+1)" contain " x^(10)`. Then,
`36-3r = 10 rArr 3r = 26 rArr r=26/3`
Since the value of r cannot be a fraction , so there is no term containing `x^(10)`.


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