olnata wrote:
Bunuel wrote:
If n is an integer greater than 1, is 3^n-2^n divisible by 35?
(1) n is divisible by 15.
(2) n is divisible by 18.
Explanation to follow.
(1) n is divisible by 15.
(2) n is divisible by 18.
Explanation to follow.
I didnt know the rule, but i solved it in the following way:
It is said that:
3^n-2^n=35a
(1) n=15b
3 has a repeated last digits when it is raised to the power
3, 9, 7, 1
2 has a repeated last digits when it is raised to the power
2, 4, 8, 6
if n = 15b -->
--> the last digit of 3^15b-2^15b = ...7 - ...8 = ....9
9 is not divisible
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