若a-b=3,则2a^2-2b^2-12b=

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若a-b=3,则2a^2-2b^2-12b=
若a-b=3,则2a^2-2b^2-12b=

若a-b=3,则2a^2-2b^2-12b=
2a^2-2b^2-12b
=2(a+b)(a-b)-12b
=2(a+b)×3-12b
=6a+6b-12b
=6a-6b
=6(a-b)
=18

a=b+3,代数，等于18