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2 votes
-1,-7,-49 nth term please help me please

2 Answers

3 votes

Answer:

a(n) =
- \frac{ {7}^(n) }{7}

User Jenita
by
8.3k points
6 votes

Answer:


a_n=(-1) \cdot 7^(n-1)

Explanation:


\boxed{\begin{minipage}{5.5 cm}\underline{Geometric sequence}\\\\$a_n=ar^(n-1)$\\\\where:\\\phantom{ww}$\bullet$ $a$ is the first term. \\\phantom{ww}$\bullet$ $r$ is the common ratio.\\\phantom{ww}$\bullet$ $a_n$ is the $n$th term.\\\phantom{ww}$\bullet$ $n$ is the position of the term.\\\end{minipage}}

Given sequence:

  • -1, -7, -49, ...

The given sequence is a geometric sequence since there is a common ratio between consecutive terms.

To calculate the common ratio, divide consecutive terms:


\implies r=(a_2)/(a_1)=(-7)/(-1)=7


\implies r=(a_3)/(a_2)=(-49)/(-7)=7

Therefore, the common ratio, r, is 7.

Substitute the found value of r and the first term, -1, into the formula to create an equation for the nth term:


\implies a_n=(-1) \cdot 7^(n-1)

User Midhun Pottammal
by
9.0k points

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