1.

Find the coefficient of `x` in the expansion of `(1 - 3x + 7x^(2)) (1 - x)^(16)`.

Answer» Given, expansion `= (1 - 3x + 7x^(2)) (1 - x)^(16)`
`= (1 - 3x + 7x^(2)) (.^(16)C_(0) 1^(16) - .^(16)C_(1) 1^(15) x^(1) + .^(16)C_(2) 1^(14) x^(2) + ....+ .^(16)C_(16) x^(16))`
`= (1 - 3x + 7x^(2)) (1 - 16 x + 120 x^(2) + ....)`
`:.` Cefficient of `x = - 3 - 16 = - 19`


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