来自刘陵顺的问题
【已知:x2+xy=12,xy+y2=15,求(x+y)2-(x+y)(x-y)的值.】
已知:x2+xy=12,xy+y2=15,求(x+y)2-(x+y)(x-y)的值.
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2020-06-20 17:12
【已知:x2+xy=12,xy+y2=15,求(x+y)2-(x+y)(x-y)的值.】
已知:x2+xy=12,xy+y2=15,求(x+y)2-(x+y)(x-y)的值.
∵x2+xy=12,xy+y2=15,
∴x2+xy+xy+y2=12+15,
∴(x+y)2=27,
x2+xy-(xy+y2)=12-15,
∴(x+y)(x-y)=-3,
∴原式=27-(-3)=30.