A.9x2﹣9xy﹣y2B.5x2﹣3xy﹣9y2C.﹣5x2+3xy+9y2D.﹣5x2﹣9xy﹣y2
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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