求证答案~~~

美小波

Q36:

If x and y are positive integers and r is the remainder when 3^{4x + 2} + y is divided by 10, what is the value of r?

(1)     x = 25

(2)     y = 1

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

我这里的答案是B，但我怎么觉得不大对啊 。。。

其实我是没思路的。。。

谢谢解答了~~

[此贴子已经被作者于2009/8/23 20:45:05编辑过]

xinhang0602

B是对的啊~~

3的N次方的尾数是以3 9 7 1 ，四个一循环的 ，那么3^{4x + 2}  的尾数就是9

那么R的确定就看9+Y 除以 10 余数咯~~

当然是知道Y就ok拉~~~~X没用

美小波

谢谢~~  终于明白了~~~