已知xy=3,x+y=7.求①x^2+xy+y^2, ②(x-y)^2的值快点,要正确,要说过程哦,谢谢了

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已知xy=3,x+y=7.求①x^2+xy+y^2,②(x-y)^2的值快点,要正确,要说过程哦,谢谢了已知xy=3,x+y=7.求①x^2+xy+y^2,②(x-y)^2的值快点,要正确,要说过程哦

已知xy=3,x+y=7.求①x^2+xy+y^2, ②(x-y)^2的值快点,要正确,要说过程哦,谢谢了
已知xy=3,x+y=7.求①x^2+xy+y^2, ②(x-y)^2的值
快点,要正确,要说过程哦,谢谢了

已知xy=3,x+y=7.求①x^2+xy+y^2, ②(x-y)^2的值快点,要正确,要说过程哦,谢谢了
①原式＝（x+y）^2－xy＝7^2－3＝46
②原式＝（x+y）^2－4xy＝7^2－4×3＝37

x^2+xy+y^2
=(x+y)^2-xy
=7*7-3
=46
②(x-y)^2
=(x+y)^2-4xy
=7*7-4*3
=37

因为
xy=3,
x+y=7
则
①x^2+xy+y^2＝（x+y)^2-xy=7×7－3＝49－3＝46
②(x-y)^2＝x^2－2xy+y^2＝（x^2＋2xy+y^2）－4xy＝（x+y)^2-4xy=49－4×3＝49－12＝37

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