How do you find a general formula for each arithmetic sequence given 8th term is -20; 17th term is -47?

Question

How do you find a general formula for each arithmetic sequence given 8th term is -20; 17th term is -47?

1 Answer

Impact of this question

2894 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-02-20T07:25:08

$n^(th)$ term of the arithmetic sequence is given by $4-3n$

Explanation:

If $a$ is the first term of an arithmetic sequence and $d$ the difference between a term and its preceding term, general formula for $n^(th)$ term of the arithmetic sequence is given by $a+(n-1)d$ .

As $8^(th)$ term is $-20$ and $17^th$ term is $-47$

$a+(8-1)d=a+7d=-20$ and $a+(17-1)d=a+16d=-47$ .

Subtracting first equation from second, we get

$9d=-47+20$ or $9d=-27$ i.e. $d=-3$

putting this in first we get $a+7*(-3)=-20$ or $a=1$ .

Hence, $n^(th)$ term of the arithmetic sequence is given by $1-3(n-1)$ or $4-3n$

Science

Math

Humanities

... and beyond

How do you find a general formula for each arithmetic sequence given 8th term is -20; 17th term is -47?

1 Answer

Explanation:

Related questions

Impact of this question