Discrete Mathematics and Its Applications, Seventh Edition

Published by McGraw-Hill Education
ISBN 10: 0073383090
ISBN 13: 978-0-07338-309-5

Chapter 4 - Section 4.1 - Divisibility and Modular Arithmetic - Exercises - Page 245: 35

Answer

If n|m, where n and m are integers greater than 1, and if a ≡ b (mod m), where a and b are integers, then a ≡ b (mod n).

Work Step by Step

To prove that if n|m, where n and m are integers greater than 1, and if a ≡ b (mod m), where a and b are integers, then a ≡ b (mod n), we can use the following steps: Given: n and m are integers greater than 1 n|m (n divides m) a ≡ b (mod m), where a and b are integers Step 1: Since n|m, there exists an integer k such that m = nk. Step 2: Because a ≡ b (mod m), we know that m|(a-b). This means there exists an integer j such that a - b = mj. Step 3: Substitute m = nk from step 1 into the equation from step 2: a - b = (nk)j Step 4: Rearrange the equation from step 3: a - b = n(kj) Step 5: Let c = kj. Since k and j are integers, c is also an integer. We can rewrite the equation from step 4 as: a - b = nc Step 6: From the equation in step 5, we can see that n|(a-b), which means a ≡ b (mod n). Therefore, we have shown that if n|m, where n and m are integers greater than 1, and if a ≡ b (mod m), where a and b are integers, then a ≡ b (mod n).
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