求x^2-4y^2/x^2+4xy+4y^2÷(x^2-2xy)的值,其中x=1,y=-2

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求x^2-4y^2/x^2+4xy+4y^2÷(x^2-2xy)的值,其中x=1,y=-2求x^2-4y^2/x^2+4xy+4y^2÷(x^2-2xy)的值,其中x=1,y=-2求x^2-4y^2/

求x^2-4y^2/x^2+4xy+4y^2÷(x^2-2xy)的值,其中x=1,y=-2
求x^2-4y^2/x^2+4xy+4y^2÷(x^2-2xy)的值,其中x=1,y=-2

求x^2-4y^2/x^2+4xy+4y^2÷(x^2-2xy)的值,其中x=1,y=-2
x^2-4y^2/x^2+4xy+4y^2÷(x^2-2xy)
=(x-2y)(x+2y)/(x+2y)²÷[x(x-2y)]
=(x-2y)/(x+2y)*1/[x(x-2y)]
=1/[x(x+2y)]
=1/[1+2×(-2)]
=-1/3