[求助]gwd 1-36 and gwd 5-11

hedgeforfun

gwd 1-Q36:
x

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2

3 4 5 6 7 8 9

On the number line, the shaded interval is the graph of which of

the following inequalities?

A. ≤ 4

B. ≤ 8

C. ≤ 4

D. ≤ 6

E. ≤ 6

答案: B, 求教解题的思路.

GWD 5-Q11:

If x is a positive integer, is the remainder 0 when 3x + 1 is

divided by 10?

(1) x = 4n + 2, where n is a positive integer.

(2) x > 4

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.

答案是A, 我觉的应为E. N为正奇数时, 余数不等于零, N 为偶数时,余数为

零..请牛牛们解释 A 的理由.

hedgeforfun

now I understand, thank you very much!

windfalls

第一题看图解不等式可得

第二题：

3 的 4n + 2 次方可写成： 3 的 4 次方 的n 次方 X 9 + 1 ，

3 的 4 次方的最后一位是1 ， 1 的 n 次方也是1 ，乘以 9 得9 ， 加上 1 就是 10 ，

这样就能被 10 除。

lemonees

题1：数轴上的范围问题，看到图就应该知道的了

题2：（1）N=1，X=6，3^6的个位数是9,加1后能被10整除; N=2, X=10,一样

(2) 不能确定被10整除

所以选A