# Sequence Q. (1 Viewer)

#### YonOra

##### Well-Known Member
Hey,

So I did this by subbing in values (rlly not efficient and time consuming). Can someone show me how they would actually solve this? Thanks

#### idkkdi

##### Well-Known Member
Hey,

So I did this by subbing in values (rlly not efficient and time consuming). Can someone show me how they would actually solve this? Thanks

View attachment 29466
each number has magnitude n with rotating +- sign. therefore B.

#### YonOra

##### Well-Known Member
each number has magnitude n with rotating +- sign. therefore B.
Ah yes, how did i over see that.

#### CM_Tutor

##### Moderator
Moderator
Note that there are several ways the answer could have been written, including:
• $\bg_white (-1)^{n-1}n$
• $\bg_white (-1)^{n+1}(n+1)+(-1)^n$
• $\bg_white (-1)^n(n+1)$ if you started at $\bg_white n=0$
I could make the MCQ harder by making (C) $\bg_white (-1)^nn$, which gives the sequence $\bg_white -1, 2, -3, 4, ...$ and (D) be a correct answer and see how many students don't notice that the alternating signs start from the wrong sign and go for (C).

#### YonOra

##### Well-Known Member
Note that there are several ways the answer could have been written, including:
• $\bg_white (-1)^{n-1}n$
• $\bg_white (-1)^{n+1}(n+1)+(-1)^n$
• $\bg_white (-1)^n(n+1)$ if you started at $\bg_white n=0$
I could make the MCQ harder by making (C) $\bg_white (-1)^nn$, which gives the sequence $\bg_white -1, 2, -3, 4, ...$ and (D) be a correct answer and see how many students don't notice that the alternating signs start from the wrong sign and go for (C).

Moderator

Moderator