7, 4, 1 find the 41st term
You asked:
Determine the \(41^{\text{th}}\) term in the sequence \(7, 4, 1, \ldots\).
MathBot Answer:
$$7,4,1,...$$The 41st term in this arithmetic sequence is $-113$.
The nth term in this sequence is given by the formula:
Explicit Formula: $$a_n=10 - 3 n$$
Recursive Formula: $$a_n=a_{n-1} - 3, \text{where } a_{1}=7$$
$$\begin{matrix}7&&4&&1\\[6pt]&-3&&-3\\[6pt]\end{matrix}$$
Explicit Formula
The formula for an arithmetic sequence where $a_1$ is the 1st term, $d$ is the common difference, and $n$ is the term number is $$a_n=a_1 + d (n - 1)$$
Find $a_1$ and $d$: $$\begin{aligned} a_1&=7 \\ d&=-3 \end{aligned}$$
The nth term rule is:$$\begin{aligned} a_n&=a_1 + d (n - 1) \\ &=7 + \left(-3\right) (n - 1) \\ &=10 - 3 n \end{aligned}$$
Recursive Formula
The formula for an arithmetic sequence where $a_{n-1}$ is the (n-1)th term, $d$ is the common difference, and $n>1$ is $$a_n=a_{n-1} + d$$
Find $d$: $$\begin{aligned} d=-3 \end{aligned}$$
The nth term rule is:$$\begin{aligned} a_n&=a_{n-1} + d \\ &=a_{n-1} + \left(-3\right) \\ &=a_{n-1} - 3 \end{aligned}$$