hey madikay.
ok lemme explain to u how i got (iv), (v) and (vi)
as itold u before use the formula
a+(n-1)d + 1/2(n-1)(n-2)c
a- 1st term
d - difference between 1st and 2nd term
c final difference(find the difference of the difference until u get a constant value)
the sequence
4 9 16 25
+5 +7 +9
+2 +2
you get 2 as the final difference
now substitute
4 + 5n -5 + ((n-1)(n-2) * 2)/2
= 4 + 5n -5 +n^2 -3n +2
= n^2 + 2n + 1
= (n+1)^2
use the same method for (v)
or if not possible try and observing the sequence very carefully and get the rule
the answer for (vi) is sequence for (iv) - sequence for (v)