# Doubt on binomial theorem

#7

(1+x)^n put x=1/3 , n=12 and add subtract C_0

#9

1+2+2^2......2^n

#10

- easiest approch is hit and trial put any value n>2

match the option

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# b??

- for finding coefficient write down general term

C_r x^{r_1}x^{r_2}..... write down cases in

u will find ans

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