Question
Download Solution PDFIt is given that 5 does not divide n - 1, n and n + 1, where n is a positive integer. Which one of the following is correct ?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
Divisibility rule of 5: A number is divisible by 5 only if the unit digit is 0 or 5.
Calculation:
Let n - 1, n & n + 1 be 6, 7 & 8.
⇒ n2 + 1 = 72 + 1 = 50
⇒ n2 - 1 = 72 - 1 = 48
⇒ n2 + n = 72 + 7 = 56
⇒ n2 - 7 = 72 - 7 = 42
∴ 5 divides n2 + 1
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