Question 36923
Well, the recursive formula depends on the previous terms and "d" (the common difference) to find the next terms.


Your pattern 3,9,15,21.
It is quite obvious the common difference (d) is 6
If it's not obvious, you can subtract {{{t[2]}}} from {{{t[1]}}} and then get your commond difference.


The recursive formula is {{{t[n]=t[n-1]+d}}}
Now just plug in the numbers.


To find the 5th term:
{{{t[5]=t[4]+6}}}
{{{t[5]=21+6}}}
{{{highlight(t[5]=27)}}}


To find the 6th term:
{{{t[6]=t[5]+6}}}
{{{t[6]=27+6}}}
{{{highlight(t[6]=33)}}}


To find the 7th term:
{{{t[7]=t[6]+6}}}
{{{t[7]=33+6}}}
{{{highlight(t[7]=39)}}}

Hope this helps!