Hey all,

I have the following statement: 5|7^k-2^k for all k in N

I want to prove it by induction, so I proceed as follows..

Basis step:

let p(k) be the statement that 7^k-2^k = 5m for m in N and k in P.

Then p(1) is the statement 7^1-2^1=5m for some m in N. This is clearly true for m = 1.

Induction step:

Suppose that p(k) is true for some k in P, That is, 7^k-2^k = 5m for some m in N, then, 7^(k+1) - 2^(k+1) = 5*1^(k+1) for k + 1 in N.

Therefore, p(k+1) is true. Hence p(k) is true for all k in P.

The basis step is straight forward, but I am not sure whether I have done the induction step correctly particularly with the result 5^(k+1). Any criticism welcome. Thanks