已知x2-xy=5,xy-y2=-3,求代数式x2-y2和x2-2xy+y2的值.这样.那个x2是x的平方的意思,2xy是2乘xy的意思,因为键盘有限,打不出来,谢谢.

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已知x2-xy=5,xy-y2=-3,求代数式x2-y2和x2-2xy+y2的值.这样.那个x2是x的平方的意思,2xy是2乘xy的意思,因为键盘有限,打不出来,谢谢.已知x2-xy=5,xy-y2=

已知x2-xy=5,xy-y2=-3,求代数式x2-y2和x2-2xy+y2的值.这样.那个x2是x的平方的意思,2xy是2乘xy的意思,因为键盘有限,打不出来,谢谢.
已知x2-xy=5,xy-y2=-3,求代数式x2-y2和x2-2xy+y2的值.这样.
那个x2是x的平方的意思,2xy是2乘xy的意思,因为键盘有限,打不出来,谢谢.

已知x2-xy=5,xy-y2=-3,求代数式x2-y2和x2-2xy+y2的值.这样.那个x2是x的平方的意思,2xy是2乘xy的意思,因为键盘有限,打不出来,谢谢.
x2-y2
=x2-xy+xy-y2
=5-3
=2
x2-2xy+y2
=x2-xy-（xy-y2）
=5-（-3）
=8

x2-y2=2
x2-2xy+y2=8

x2-y2=2 x2-2xy+y2=8

x2-y2
=x²-xy+xy-y²
=5-3
=2
x2-2xy+y2
=x²-xy-xy+y²
=x²-xy-(xy-y²)
=5+3
=8

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