已知x²-xy=5,xy-y²=-3,求代数式x²-y²和x²-2xy+y²
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已知x²-xy=5,xy-y²=-3,求代数式x²-y²和x²-2xy+y²
已知x²-xy=5,xy-y²=-3,求代数式x²-y²和x²-2xy+y²
已知x²-xy=5,xy-y²=-3,求代数式x²-y²和x²-2xy+y²
式一加式二,得第一个答案,2
式一减式二,得第二个答案,8
x²-xy=5……①
xy-y²=-3……②
①+②得:
x²-y²=2
①-②得:
x²-2xy+y²=5-(-3)=5+3=8