MathLabs

Problem 1

(a) Find all positive integers nn for which 2n−12^n-1 is divisible by 77. (b) Prove that no positive integer nn makes 2n+12^n+1 divisible by 77.
Step 4 of 4: State the answer
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n=3k (k≥1)n=3k\ (k\ge1)
Detailed analysis

Therefore part (a) has exactly n=3,6,9,…n=3,6,9,\ldots, while part (b) has no positive-integer solution.