1.

If n is a natural number then 73n – 43n is always divisible by …(1) 11(2) 3 (3) 33 (4) both 11 and 3

Answer»

(4) both 11 and 3

73n – 43n is of the form a2n – b2n which is divisible by both a – b and a + b. So 73n – 43n is divisible by both 7 – 4 = 3 and 7 + 4 = 11.



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