Can 7 divide 3^(2n+1) + 2^(n+2) in induction for number theory?

mcooper
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Homework Statement



Show 7 divides 3^(2n+1) + 2^(n+2)

The Attempt at a Solution



Have proved base case K=1 and for the case k+1 I have got ot the point of trying to show 7 divides 9.3^(2k+1) + 2.2^(k+2).

Any pointers would be much appreciated. Thanks in advance
 
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Well, you don't seem to have even stated the inductive hypothesis yet, let alone tried doing something with it.
 
The inductive hypothesis is that 7 divides 3^(2k+1) + 2^(k+2)
 
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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