{2,5}是A∩B的子集{2,5}一定是A的子集观察A集合有数字2a^3-2a^2-a+7=5a^3-2a^2-a+2=0a^2(a-2)-(a-2)=0(a+1)(a-1)(a-2)=0,a=1,-1,2用B集合检验a=1时,a+1=2,a^2-2a+2=1,有重复,不行a=-1时,a+1=0,a^2-2a+2=5,-1/2(a^2-3...