If \[{{a}_{r}}\] is the coefficient of \[{{x}^{r}}\], in the expansion of \[{{(1+x+{{x}^{2}})}^{n}}\], then \[{{a}_{1}}-2{{a}_{2}}+3{{a}_{3}}-....-2n\,{{a}_{2n}}=\] [EAMCET 2003]

If \[{{a}_{r}}\] is the coefficient of \[{{x}^{r}}\], in the expansi

1.	If \[{{a}_{r}}\] is the coefficient of \[{{x}^{r}}\], in the expansion of \[{{(1+x+{{x}^{2}})}^{n}}\], then \[{{a}_{1}}-2{{a}_{2}}+3{{a}_{3}}-....-2n\,{{a}_{2n}}=\] [EAMCET 2003]
A.	0
B.	n
C.	? n
D.	2n
Answer» D. 2n

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If \[{{a}_{r}}\] is the coefficient of \[{{x}^{r}}\], in the expansion of \[{{(1+x+{{x}^{2}})}^{n}}\], then \[{{a}_{1}}-2{{a}_{2}}+3{{a}_{3}}-....-2n\,{{a}_{2n}}=\] [EAMCET 2003]

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