满足M包含于{a1,a2,a3,a4},且M交{a1,a2,a3}={a1,a2}的集合M为?
问题描述:
满足M包含于{a1,a2,a3,a4},且M交{a1,a2,a3}={a1,a2}的集合M为?
答
{a1.a2}或{a1.a2.a4}
答
M={a1,a2,a4}或{a1,a2}