3(a-b+1)-4(1/2a-b+1/4),其中a+b=-1

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3(a-b+1)-4(1/2a-b+1/4)
=3a-3b+3-2a+4b-1
=a+b+2
=-1+2
=1

3(a-b+1)-4(1/2a-b+1/4)
=3a-3b+3-(2a-4b+1)
=3a-3b+3-2a+4b-1
=a+b+2
=-1+2
=1