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Please solve last 2 question in detail.

Q.13. Show that ${9}^{n+1}-8n-9$ is divisible by 64, whenever n is a positive integer.

Q.14. Prove that $\sum _{r=0}^{n}{3}^{r}{}^{n}C_{r}={4}^{n}$.

Refer the link for the answer to your query:

**Q 13.**https://www.meritnation.com/ask-answer/question/using-binomial-theoram-show-that-9n-1-8n-9-is-divisible-by-6/binomial-theorem/3767333

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