對(duì)非負(fù)實(shí)數(shù)x“四舍五入”取整數(shù)的值記為[x].如：[0]=[0.48]=0,[0.64]=[1.493]=1...(1)填空：
對(duì)非負(fù)實(shí)數(shù)x“四舍五入”取整數(shù)的值記為[x].如：[0]=[0.48]=0,[0.64]=[1.493]=1...
(1)填空：[3.12]=?,[11.89]=?
(2)判斷[x+y]=[x]+[y]是否一定成立?若一定成立,請(qǐng)證明；若不一定成立,請(qǐng)舉一個(gè)反例；
(3)如果[x]=3,則實(shí)數(shù)x的取值范圍為( )；求滿足[x]=3/4x的非實(shí)數(shù)x值