3/(1-x)∈Z,
所以 1-x=1,3,-1,-3
解得 x=0,-2,2,4
从而 A={0,-2,2,4}
它的非空真子集有2⁴-2=14个.
分别是{0}、{－2}、{2}、{4}、{0,－2}、{0,2}、{0,4}、{－2,2}、{－2,4}、{2,4}
{0,－2,2}、{0,－2,4}、{0,2,4}、{－2,2,4}.