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If x, y and z are real numbers such that: x + y + z = 5 and xy + yz + zx = 3. What is the largest value that any of the numbers can have?

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Biggest Bendy

Four rods are hinged at their ends to form a quadrilateral. How can you maximise its area?

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Investigate the graphs of y = [1 + (x - t)^2][1 + (x + t^)2] as the parameter t varies.

Three Ways

Age 16 to 18 Challenge Level:

Given that $x + y = -1$ find the largest value of $xy$

  1. by coordinate geometry.
  2. by calculus.
  3. by algebra.