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How many noughts are at the end of these giant numbers?

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Mod 3

Prove that if a^2+b^2 is a multiple of 3 then both a and b are multiples of 3.

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Common Divisor

Find the largest integer which divides every member of the following sequence: 1^5-1, 2^5-2, 3^5-3, ... n^5-n.

Number Rules - OK

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

image of colourful numbers.Can you convince me of each of the following?

  • The pattern below continues forever: $$8^2 = 7^2 + 7 + 8$$ $$9^2 = 8^2 + 8 + 9$$
  • If a square number is multiplied by a square number the product is ALWAYS a square number.
  • No number terminating in $2, 3, 7$ or $8$ is a perfect square.