Nth Term it just doesn't seem to work?

Question

-1,1,3,5,9 what the nth term please?

theres no 7 meant to be in the middle (5,9) this question is from a text book!

Answer 1

if there is 7 between 5,9 it will be good : ))

Answer 2

Must have missed 7 between 5 and 9. If we consider 7 to be there then its an Arithmatic Progression.
Whose nth Term = First Term + [ (n-1). common difference ]
Here First Term = -1 and common difference is = 1 - (-1) =2
Hence nth term in our case = (-1)+(n-1).2 = -1+2n-2 = 2n-3 .. Answer

Answer 3

Not a real answer here, but I suspect that with this set of numbers, there are several possibilities for the next term, and hence the solution. I may be wrong.
It can't be arithmetic because in an arithmetic sequence the interval between the numbers is constant, and is the coefficient of the nth term in the general expression.

Answer 4

we know that the formula for nth term in A.P.=a+(n-1)d
a=first term,n=no.of term,d=common difference
in this problem a= -1,d=second term-first term=1-(-1)=1+1=2,n=n
so nth term= -1+(n-1)2
= -1+2n-2
= 2n-3
but you forgot 7 after 5

Answer 5

If you did really mean -1,1,3,5,9 (i.e without the 7) then a possible solution is:

2n-3 + (n-1)(n-2)(n-3)(n-4)/12

Note that these would also work:

2n-3 + (n-1)(n-2)(n-3)(n-4)/12 + (n-1)(n-2)(n-3)(n-4)(n-5)*c
where c is any number you like

Answer 6

--1, 1, 3, 5, 7, 9, ...
it is simple arithmetic progression.
you get 1st term --1 = --1 + (1 --1)*2
2nd term 1 = --1 + (2 --1)*2
3rd term 3 = --1 + (2 --1)*2
4th term 5 = --1 + (3 --1)*2
..................................................
nth term = --1 + (n --1)*2 = 2n --3.

Answer 7

N = - 1 - (13/6)n + (35/12)n^2 - 5/6)n^3 + (1/12)n^4
N = - 1 - (n/6)(13 - (35/2)n + 5n^2 - (1/2)n^3)
N = - 1 - (n/6)(13 - n(35/2 + 5n - (1/2)n^2)
N = - 1 - (n/6)(13 - (n/2)(35 + n(10 - n)))

Answer 8

2n-3

Answer 9

tn =_1+(n_1)2=2n_3