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问题: 初一

先化简.在求值:
5ab-2{ab-2[1/4-1/2(ab-3ab)-2ab]}-(4ab-1).其中
|a-2|+(b+3))=0


解答:

5ab-2{ab-2[1/4-1/2(ab-3ab)-2ab]}-(4ab-1)
=5ab-2{ab-2[1/4-1/2*(-2ab)-2ab]}-(4ab-1)
=5ab-2[ab-2(1/4+ab-2ab)]-(4ab-1)
=5ab-2(ab-1/2+2ab)-(4ab-1)
=5ab-2(3ab-1/2)-(4ab-1)
=5ab-6ab+1-4ab+1
=2-5ab
因为|a-2|+(b+3)=0
所以a-2=0,b+3=0
所以a=2,b=-3
所以原式=2-5ab=2+30=32