Stage: 4 Challenge Level: 
Investigate the areas of squares formed by joining points on a square grid and show that it is impossible to construct any square whose area is (4n + 3) where n is an integer.
Long problems. Divisibility. Pythagorean triples. Number theory. Modulus arithmetic. Pythagoras' theorem. Circles. Mathematical reasoning & proof. Index notation/Indices. Factors and multiples.
Published May 1999,November 2008,December 2008.
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