Question

If the common difference of an AP is 3, find the value of $a_{17}-a_{12}$.

Answer 1

Given common difference $d=3$

then

$a_{17}-a_{12}=a+16d-(a+11d)$

$=a+16d-a-11d$

$=5d=5\times 3$

$[a_{17}-a_{12}=15]$.