Question

Решите системы:
1)$\left \{ {{\frac{x+y}{x^{2}-y^{2} } =\frac{1}{4} } \atop {xy=21}} \right.$
2)$\left \{ {{x+y=2} \atop {xy=-8}} \right.$
3)$\left \{ {{x^{2}+y^{2} =25} \atop {x-y=-1}} \right.$

Answer 1

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