下列去括号(或添括号)运算:①3m-[5n-(2p-1)]=3m-5n+2p-1②-(3m-2)-(-n+p)=-3m-2+n+p③3xy-5x2y-2xy2+1=3xy-[5x2y+(2xy2-1)

题目简介

下列去括号(或添括号)运算:①3m-[5n-(2p-1)]=3m-5n+2p-1②-(3m-2)-(-n+p)=-3m-2+n+p③3xy-5x2y-2xy2+1=3xy-[5x2y+(2xy2-1)

题目详情

下列去括号(或添括号)运算:
①3m-[5n-(2p-1)]=3m-5n+2p-1
②-(3m-2)-(-n+p)=-3m-2+n+p
③3xy-5x2y-2xy2+1=3xy-[5x2y+(2xy2-1)]
④x3-5x2-4x+9=9-(5x2+4x-x3
其中正确的个数是(  )
A.1个B.2个C.3个D.4个
题型:单选题难度:中档来源:不详

答案

①3m-[5n-(2p-1)]=3m-5n+2p-1,去括号正确,故本项正确;
②-(3m-2)-(-n+p)=-3m+2+n+p,去括号错误,故本项错误;
③3xy-5x2y-2xy2+1=3xy-[5x2y+(2xy2-1)],添括号正确,故本项正确;
④x3-5x2-4x+9=9-(5x2+4x-x3),添括号正确,故本项正确;
综上可得:①③④正确,共3个.
故选C.

更多内容推荐