问题 解答题

化简:

(1)5a2-[a2+(5a2-2a)-2(a2-3a)];

(2)(8xy-x2+y2)-(x2-y2+8xy).

答案

(1)原式=5a2-a2-5a2+2a+2a2-6a=a2-4a;

(2)原式=8xy-x2+y2-x2+y2-8xy=2y2-2x2

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