解:
(3A﹣2B)﹣(2A+B)=3A﹣2B﹣2A﹣B=A﹣3B,
当A=4x2+5xy﹣2y2,B=x2+xy﹣y2时,
A﹣3B=(4x2+5xy﹣2y2)﹣3(x2+xy﹣y2)=4x2+5xy﹣2y2﹣3x2﹣3xy+3y2=x2+2xy+y2,
当x=,y=﹣1时,
原式=()2+2××(﹣1)+(﹣1)2=﹣1+1=.
计算或化简:
①;
②;
③;
④﹣12006﹣(1﹣0.5)×[3﹣(﹣3)2];
⑤3x2y﹣4xy2﹣3+5x2y+2xy2+5;
⑥3(2x2﹣y2)﹣2(3y2﹣2x2);
⑦先化简再求值:﹣2y3+(2x3﹣xyz)﹣2(x3﹣y3+xyz),其中x=1,y=2,z=﹣3.
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