Question

Find the 25 term of the arithmetic sequence whose common difference is d=2 and whose first term is a = - 4.

Answer 1

Solution

- The formula for the nth term of an arithmetic sequence is

$\begin{gathered} a_n=a+(n-1)d \\ where, \\ a=\text{ First term} \\ d=\text{ Common difference} \\ n=\text{ Number of terms} \end{gathered}$

- We have been given:

$\begin{gathered} a=-4 \\ d=2 \\ n=25 \end{gathered}$

- Thus, the 25th term is

$\begin{gathered} a_{25}=-4+(25-1)(2) \\ a_{25}=-4+24(2) \\ a_{25}=-4+48 \\ \therefore a_{25}=44 \end{gathered}$