For every positive integer n, prove that `7^n-3^n`is divisible by 4.

Explanation

To prove that \(7^n - 3^n\) is divisible by 4 for every positive integer \(n\), we will use the principle of mathematical induction.

### Step 1: Base Case
We start with the base case \(n = 1\).

\[ 7^1 - 3^1 = 7 - 3 = 4 \]
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