Q13/035)Prove that 8^91 > 7^92?

Proof:

8 = 7 + 1
= 7(1+ 1/7)

8^91 = 7^91( 1+1/7)^91

now (1+ 1/7)^ 91 > 1 + 1/7*91 ignoring rest parts after binomial expansion as (1+a)^n > 1+na

> 1 + 13 > 14

so 8^91 ? 7^91* 14 > 7^91 *7 or 7^92 ( actually it is greater than 2 * 7^92)