6 (a) The first five terms of a sequence are 17, 11, 5, −1, −7. Find, in terms of n, an expression for the nth term of this sequence. (b) The nth term, Sn , of a different sequence is found using the formula Sn =n^2+3n. (i) Work out the first four terms of this sequence. (ii) The nth term, Tn , of another sequence is found using the formula Tn = 5n – 12 . There are two values of n for which Sn/Tn=6 Form and solve an equation in n to find these two values.