Question

Write the term to term rule, position-to-term (nth term) and 20thterm of the sequence 3, -1 ,-5, -9, -13 ,....​

Answer 1

It's a arithmetic sequence

• First term=a=3
• common difference=d=-1-3=-4

Nth term rule:-

$\\ \rm\Rrightarrow a_n=a+(n-1)d$

$\\ \rm\Rrightarrow a_n=3+(n-1)-4$

$\\ \rm\Rrightarrow a_n=3-4n+4$

$\\ \rm\Rrightarrow a_n=7-4n$

20th term

$\\ \rm\Rrightarrow a_{20}=7-80=-73$