The maximum value of real numbers x, y satisfying X & sup2; + Y & sup2; - 2x-4y-20 = 0, X & sup2; + Y & sup2; is

The maximum value of real numbers x, y satisfying X & sup2; + Y & sup2; - 2x-4y-20 = 0, X & sup2; + Y & sup2; is

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