x-y=1,xy=3 求 x^3+y^3

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x-y=1,xy=3 求 x^3+y^3

x+y =± √ (x+ y) =± √[ (x-y) +4xy ] =± √13 x^3+y^3 =(x+y)(x -xy+y ) =(x+y)[(x-y) + xy)] = ± √13 (1+3) = ± 4√13