3a45a7
幼苗
共回答了13个问题采纳率:84.6% 举报
因为:la+b-3l+(ab+2)^2=0,且la+b-3l≥0,(ab+2)^2≥0,所以:la+b-3l=0,(ab+2)^2=0a+b-3=0,ab+2=0即:a+b=3,ab=-2 (2a-b+1)(2a-b-1)-(a+2b)(a-b)=[(2a-b)??-1]-(a??-ab+2ab-2b??)
=4a??+b??-4ab-1-a??-ab+2b??
=3a??+3b??-5ab-1=3(a??+b??)-5ab-1=3[(a+b)??-2ab)]-5ab-1=3(a+b)??-11ab-1=3*3??-11*(-2)-1=50
1年前
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