(x-5y)(-x-5y)-(-x-5y)^2其中x=-1,y=-0.5

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(x-5y)(-x-5y)-(-x-5y)^2其中x=-1,y=-0.5

(x-5y)(-x-5y)-(-x-5y)²
=-(x-5y)(x+5y)-(x+5y)²
=-(x+5y)[(x-5y)+(x+5y)]
=-2x(x+5y)
=-2x²-10xy
=-2×(-1)²-10×(-1)×(-0.5)
=-2-5
=-7
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