2.已知A={2,-1,X的平方-X+1},B={2y,-4,X+4},C={-1,7},且A交B=C,求X,y的值及A并B.
设n是大于1的数,求证,在数1,2,3,4,……,n-1,n的前面添加+或-,进行加法运算,总能使所得的和为0或1.华东师范大学出版社,2,8【2】,探索天地第六题.
【200零件,甲单独5h,甲与乙合作4h,完成,甲1h比乙多2零件,甲,乙1h各做多少?方程解要加工200个零件,甲单独做5小时,然后又和乙,完成[一共9小时],甲每个小时比乙多做2个,2人每个小时各做多少】
【下面这些单词的音节有几个festival,basketball,juice,careful,wallet,wallet,minute,expensive,pretty,bookshop,pay,however,supermarket,January,time,food,lantern,interesting,seldom,keep,tired,high,however,expensive,without,amount,little,inside,t】