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
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