Question

IF $a_n$ denotes the nth term of the AP 2, 7, 12, 17, ..., find the value of $(a_{30}-a_{20})$.

Answer 1

We have a = 2 ; d = 5

now, $a_{30}=a+(30-1)d=2+29\times 5=2+145=147$

$a_{20}=a+19d=2+19\times 5=2+95=97$

now, $a_{30}-a_{20}=147-97=50$