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"Find a formula for the nth term of this quadratic sequence: 3,5,9,15"

2. (Original post by jessicaharker51)

"Find a formula for the nth term of this quadratic sequence: 3,5,9,15"

If you're given that it's a quadratic sequence then you know that where xn is the nth term. (Eg x1 = 3, given when you put n = 1 into the formula on the right) and you need to find a, b and c.

so think about that, plus the information you're given, and see if you can work out what the sequence is

I guess you can cut down work by considering the difference between each term, and how that leaves you with less simultaneous equations to work with.
3. (Original post by jessicaharker51)

"Find a formula for the nth term of this quadratic sequence: 3,5,9,15"

Can you see what you can do from there to find a, b and c??
4. There is an easier way to do it than methods above but it's very difficult and awkward to write how to do it.

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