计ç®ï¼(5xy^2 +5xy-7x)-(4xy^2-7x +5xy^2)
=5XY^2+5XY-7X-4XY^2+7X-5XY^2
=(5-4-5)XY^2+5XY
=-4XY^2+5XYï¼
ç±6X-1=2ï¼å¾X=0.5ï¼ç±Y^2=2ï¼å¾Y=±â2ï¼
å½X=0.5ï¼Y=â2æ¶ï¼åå¼=-4Ã0.5Ã2+5Ã0.5Ãâ2=-4+5â2/2ï¼
å½X=0.5ï¼Y=-â2æ¶ï¼åå¼=-4Ã0.5Ã2+5Ã0.5Ã(-â2)=-4-5â5/2ã
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