若x-y=1,则x方-y方-2y-5=

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若x-y=1,则x方-y方-2y-5=若x-y=1,则x方-y方-2y-5=若x-y=1,则x方-y方-2y-5=x方-y方-2y-5=(x+y)(x-y)-2y-5=(x+y)×1-2y-5=x+y

若x-y=1,则x方-y方-2y-5=
若x-y=1,则x方-y方-2y-5=

若x-y=1,则x方-y方-2y-5=
x方-y方-2y-5
=(x+y)(x-y)-2y-5
=(x+y)×1-2y-5
=x+y-2y-5
=x-y-5
=1-5
=-4

x^2-y^2-2y-5
=(x+y)(x-y)-2y-5
=x+y-2y-5
=x-y-5
=1-5
=-4

(x+y)(x--y)-2y-5
=x+y-2y-5
=x-y-5
=-4