Question

If 9th term of an AP is 15 and the common difference is 2, the 1st term of the AP is

• A. 1
• B. 0
• C. -1
• D. 2

Answer 1

The correct option is C

-1

If the first term is $a$, the common difference is $d$ and the 9th term is $a_9$, then,
$a_n=a+(n-1)d$
$d=2$, $a_9=15$ and $n=9$
$\Rightarrow a+(9-1)2=15$
$\Rightarrow a+16=15$
$a=-1$