【单选题】《射雕英雄传》里黄药师在面对痴恋郭靖的女儿时吟诵西汉贾谊的“天地为炉兮,造化为工。阴阳为炭兮,万物为铜”,他的意思是
【单选题】下列各组物质中,前者属于单质、后者属于混合物的是( )
【单选题】Which of these is not a legitimate example of Commutation? A.R v P commutes to P v R B.R→P commutes to P→R C.R & P commutes to P & R
【简答题】已知二次函数f(x)=ax 2 +x有最小值,不等式f(x)<0的解集为A. (1)求集合A; (2)设集合B={x||x+4|<a},若集合B是集合A的子集,求a的取值范围.
【单选题】若集合A={(1,2),(3,4)},则集合A的真子集个数是( )
【单选题】______ we have all the materials ready, we should begin the new task at once.
【简答题】Show that each of these conditional statements is a tautology by using truth tables. a) (p ∧ q) → p b) ¬ p → (p → q) c) ¬ (p → q) → p