设全集为R,则命题a∈(1,5)的否定为a∈______.
问题描述:
设全集为R,则命题a∈(1,5)的否定为a∈______.
答
设全集为R,则命题a∈(1,5)的否定为a∈(+∞,1]∪[5,+∞)
答
(负无穷,1]∪[5,正无穷)
答
a∈(-∞,1]∪[5,+∞)