Question

Show that the progression $3,9,15,21,...$ is an AP. Write down its first term and the common difference.

• A. $6$ and $6$
• B. $5$ and $3$
• C. $3$ and $6$
• D. $6$ and $3$

Answer 1

Answer: (C)

$3$ and $6$

$a_1=3,a_2=9,a_3=15,$

$a_2-a_1=9-3=6$

$a_3-a_2=15-9=6$

$\therefore a_n-a_{n-1}=6$

$\therefore AP$ with $d=6$

first term $=3$