t1 is 23 and tn=tn-1 -3

so t2=t1 -3 (here n=2) => 20
t3=t2 -3 => 20-3=17 and so on...

so the series would be less than 3 for every next no. i.e.
t2=20; t3=17 and so on....so the value i.e. -4 would be for t10. if you go on subtracting every time 3 from the previous no. you would get it as term 10.


Amit

Thanks.

Simpler way, Use AP formula

Nth term = a + (n-1)*d

V, a = 1st term
N = the number of term you are looking for ( it you are looking for 9th term, N=9)
D = difference between two subsequent term ( in increasing order : so basically the {(nth term) - (n-1)th term}

For this particular one, we get

-4 = 23 + (n-1)*-4

solve n = 10;