若(x-y)²=7,(x+y)²=5,则x²+y²=?最好有个步骤,

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若(x-y)²=7,(x+y)²=5,则x²+y²=?最好有个步骤,

若(x-y)²=7,(x+y)²=5,则x²+y²=?最好有个步骤,
若(x-y)²=7,(x+y)²=5,则x²+y²=?最好有个步骤,

若(x-y)²=7,(x+y)²=5,则x²+y²=?最好有个步骤,