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By principle of mathematical induction, 2^4n-1 is divisible by which of the following?(a) 8(b) 3(c) 5(d) 7I have been asked this question in unit test.Enquiry is from The Principle of Mathematical Induction in section Principle of Mathematical Induction of Mathematics – Class 11

Answer»

The correct option is (a) 8

Best explanation: P(n) = 2^4n – 1

P(1) = 2^3 = 8

Let us assume P(k) is divisible by 8 and can be written as 8C, where C is any integer.

P(k) = 2^4k – 1 = 8c

P(k + 1) = 2^4(k + 1) – 1

P(k + 1) = 2^4k + 3

P(k + 1) = 2^4 . 2^4k – 1

P(k + 1) = 2^4 . 8c

Clearly, P(k + 1) is divisible by 2, 4, 8 and 16.



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