求解两道题！谢谢

wechinas

 

If n is a positive integer and r is the remainder when (n – 1)(n + 1) is divided by 24, what is the value of r?

(1)     2 is not a factor of n.

(2)     3 is not a factor of n.

                                                                                                                              

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.

不太熟悉这种表达方式。 t₁, t₂, t₃, …, t_n, …, t_n+1 = t_n / 2这是什么意思呢？

In the sequence of nonzero numbers t₁, t₂, t₃, …, t_n, …, t_n+1 = t_n / 2 for all positive integers n.  What is the value of t₅?

(1)     t₃ = 1/4

(2)     t₁ - t₅ = 15/16

                                                                                                                              

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.

yumeeiko

第一题 不知道怎么解 只知道综合1和2得出 R是偶数并是三的倍数 那么就有3个解 6 12 18 然后排出法 但是算不清楚 请高人指点

第二题 是D 吧 等比数列 t_n+1 = t_n / 2