1+（-2）+3+（-4）+......+2003+（-2004）= (1 - 2) + (3 - 4) + ... + (2003 - 2004)= -1002
小子你想抄作业？作弊的猪！！
1232x-29486y=5783698x=?
5y+2x-(5y-2x)=5y+2x-5y+2x=4x
