(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.

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(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.(x-2y)(x+2y)-(x-2y)

(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.
(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.

(x-2y)(x+2y)-(x-2y)²,其中x=-2,y=1/2.
(x-2y)(x+2y)-(x-2y)²
=(x-2y)(x+2y-x+2y)
=4y(x-2y)
=2×(-2-1)
=-6

-6

(x-2y)(x+2y)-(x-2y)²
=(x-2y)(x+2y-x+2y)
=(x-2y)×4y
当x=-2,y=1/2时,
原式=(-2-1)×[4×(1/2)]
=(-3)×2
=-6