∴x2-2x=5,
∴2x2-4x-5=2(x2-2x)-5=2×5-5=5;
(2)∵3x+4y-6x-1-y=-3x+3y-1=-3(x-y)-1,
∴-3(x-y)-1=0,
解得x-y=-
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故答案为:(1)5;(2)-
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(3)1-2(a+ab)+(ab-2b)=1-2a-2ab+ab-2b=1-2(a+b)-ab,
∵a+b=A,ab=A+2011,
∴1-2A-A-2011=3A,
解得A=-335,
所以,a+b=-335,
ab=-335+2011=1676.
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