# Thread: recent gcse question - i can't work it out!

1. ## recent gcse question - i can't work it out!

I am doing A level maths at the moment, but can't seem to work this out at all :S help would be much appreciated!!
It was to find a rule for this sequence:
when n=1, x=3
when n=2, x=6
when n=3, x=7
when n=4, x=-2

If you can help me, thank you!
Becky

2. Sorry I don't mean to be rude, just thought I'd say please let me know as soon as possible because it's driving me mad lol!
Thank youuuu

3. Hello, Becky!

Find a rule for this sequence: . $3,\:6,\:7,\:\text{-}2,\:\cdots$
There is no simple pattern to the sequence.
. . [If there is one, I've missed it.]

There is an infinite number of polynomial functions
. . that contain the four points: . $(1,3),\;(2,6),\;(3,7),\;(4,-2)$.

The simplest is a cubic: . $f(n) \:=\:-\frac{4}{3}n^3 + 7n^2 - \frac{26}{3}n + 6$