先合并同类项在求值,2x^2-4xy-1/2y^2-2x^2-1+1/2y^2其中x=2,y=- 1/4
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![先合并同类项在求值,2x^2-4xy-1/2y^2-2x^2-1+1/2y^2其中x=2,y=- 1/4](/uploads/image/z/10191913-25-3.jpg?t=%E5%85%88%E5%90%88%E5%B9%B6%E5%90%8C%E7%B1%BB%E9%A1%B9%E5%9C%A8%E6%B1%82%E5%80%BC%2C2x%5E2-4xy-1%2F2y%5E2-2x%5E2-1%2B1%2F2y%5E2%E5%85%B6%E4%B8%ADx%3D2%2Cy%3D-+1%2F4)
先合并同类项在求值,2x^2-4xy-1/2y^2-2x^2-1+1/2y^2其中x=2,y=- 1/4
先合并同类项在求值,2x^2-4xy-1/2y^2-2x^2-1+1/2y^2其中x=2,y=- 1/4
先合并同类项在求值,2x^2-4xy-1/2y^2-2x^2-1+1/2y^2其中x=2,y=- 1/4
2x^2-4xy-1/2y^2-2x^2-1+1/2y^2
=-4xy--1
=-4*2*(-1/4)-1
=2-1
=1
-4xy - 1 = -4 * 2*(-1/4) = 2