First thing I guess is to label the equation;Use Proof by Mathematical induction to prove that 7^n + 2 is divisible by 3 for all n in the Natural Numbers.

$\displaystyle p(n) = 7^n + 2$

And then Show that it holds for n=1:

$\displaystyle p(1) = 7^1 + 2$

$\displaystyle p(1) = 9$

So it works for 1; 9 is divisible by 3.

Now for p(n+1)...

$\displaystyle p(n+1) = 7^{n+1} + 2$

$\displaystyle p(n+1) = 7 \cdot 7^{n} + 2$

Now how do I go about showing that that's divisible by 3?