作业帮4xy-[(x^2+5xy-y^2)-2(x^2+3xy-1/2y^2)]其中:x=-1,y=2
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![4xy-[(x^2+5xy-y^2)-2(x^2+3xy-1/2y^2)]其中:x=-1,y=2](/uploads/image/z/978604-52-4.jpg?t=4xy-%5B%28x%5E2%2B5xy-y%5E2%29-2%28x%5E2%2B3xy-1%2F2y%5E2%29%5D%E5%85%B6%E4%B8%AD%3Ax%3D-1%2Cy%3D2)
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4xy-[(x^2+5xy-y^2)-2(x^2+3xy-1/2y^2)]其中:x=-1,y=2
4xy-[(x^2+5xy-y^2)-2(x^2+3xy-1/2y^2)]其中:x=-1,y=2
4xy-[(x^2+5xy-y^2)-2(x^2+3xy-1/2y^2)]其中:x=-1,y=2
原式=4xy-(x²+5xy-y²-2x²-6xy+y²)
=4xy-(-x²-xy)
=4xy+x²+xy
=x²-5xy
=(-1)²-5×(-1)×2
=11