Finding a closed form of the following

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Homework Statement



Create a closed form for:
ƒn = 14ƒn − 1 − 32ƒn − 2 + 24ƒn − 3

Homework Equations



Initial conditions:
ƒ(0) = 2
ƒ(1) = 5
ƒ(2) = 11

The Attempt at a Solution



Because it's 3rd order, it has me confused as how to start it. I was thinking something along the lines of C1n, C2n-1 like you would for say, the Fibonacci Sequence, but I'm not entirely sure. What are the first few steps in solving this and the method involved?
 
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What techniques do you have available? Do you know about generating functions?
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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