Question

In an arithmetic sequence , if 17 is the 3rd term, -25 is the 17th term , then which term is -1 ?

• A. 9
• B. 10
• C. 11
• D. 12

Answer 1

Answer:

A. 9

$a_n=a+(n-1)d$

$a+2d=17$

$a+16d=-25$

$14d=-42$

$d=-42/14=-3$

$a-6=17$

$a=23$

$a+(n-1)d=-1$

$23+(n-1)-3=-1$

$23+(n-1)3=-24$

$n-1=8$

$n=9$