若A=x2-2xy+y2,B=x2+2xy+y2,则4xy=( )A.B-AB.B+AC.A-BD.2A-2B
题型:单选题难度:一般来源:不详
若A=x2-2xy+y2,B=x2+2xy+y2,则4xy=( ) |
答案
∵A=x2-2xy+y2,B=x2+2xy+y2, ∴B-A=(x2+2xy+y2)-(x2-2xy+y2)=x2+2xy+y2-x2+2xy-y2=4xy, 则4xy=B-A. 故选A |
举一反三
若a-b=3,d+c=4,则(b+c)-(a-d)=______. |
若a+b=3,ab=-2,则(4a-5b-3ab)-(3a-6b+ab)=______. |
求值:2a-3(a-2b)-5(2a-b),其中a=1,b=-5. |
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