If m and n are integers divisible by 7, which of the following is not necessarily true?
Explanation:
Let m = 7a and n = 7b (both are multiples of 7)
Option (a): m – n = 7(a - b) is divisible by 7. Option (b): m2 – n2 = 49(a2 - b2) is divisible by 49. Option (c): m + n = 7(a + b) is divisible by 14 only when (a + b) is even.
∴ Option (c) is not necessarily true.
Hence, option (c).
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