prep DS test1-8

[greecechii]

8. 563-!-item-!-187;#058&000364
If n and m are positive integers, what is the remainder when 3^(4n + 2 + m) is divided by 10 ?

(1) n = 2

(2) m = 1

答案是B

請問這一題該如何看?謝謝~~

[greecechii]

從CD上得到解答了

3^1=3

3^2=9

3^3=*7

3^4=*1

3^5=**3

可見第四個等於第一個

所以n的取值沒有影響

所以選（2）

[eced]

3^(4n + 2 + m) =9* 3^4n *3^m
3^4n=81^n 不論n多少,個位數皆為1, 所以只要看 3^m即可