To find the pattern we need to subtract the given integers.
Thus, we ned to subtract the 2nd term from the 1st rems and 3rd from 2nd and so on...
⇒(-3)-(-1)=-2
Now,
(-1)-3= -4
Now,
3-9=-6
Now the defferences between the given terms are, -2, -4, -6
So here we see the difference between the terms are mutiples of 2 increasing according to their places, but interestingly we are not actually subtracting from any of the terms to get the next number, we are adding as you can see it in the last 2 terms 3&9 as only when we add 6 to 3 we get 9 and not when we subtract, so the pattern will be,
