设集合A{x/(x-3)(x-a)=0,a属于R},B={x/(x-4)(x-1）=0},求A并B,A交B.

讨论：若a=3,则A={3},B={4,1},A并B={3,4,1},A交B=空集若a=4,则A={3,4},B={4,1},A并B={3,4,1},A交B={4}若a=1,则A={3,1},B={4,1},A并B={3,4,1},A交B={1}其余情况,A={3,a},B={4,1},A并B={3,a,4,1},A交B=空集