3.命题:“若,则”的逆否命题是
A.若,则,或 | B.若,则 |
C.若,或,则 | D.若,或,则 |
已知全集,若函数,集合N=
,则=
A. | B. | C. | D. |
设全集U={1,3,5,6,8},A={1,6},B={5,6,8},则(CUA)∩B=
(A){6} (B){5,8} (c){6,8} (D){3,5,6,8}
如果U={x|x是小于9的正整数},A={1,2,3,4},B={3,4,5,6},那么CUA∩CUB=
A.{1,2} | B.{3,4} | C.{5,6} | D.{7,8} |