因为B包含于A
所以 a² - a + 1 = 3 或 a² - a + 1 = a
(1)当a² - a + 1 = 3时,
(a + 1)(a - 2) = 0
a = -1 或 a = 2
(2)当 a² - a + 1 = a 时
(a - 1)²枯烂 = 0
a = 1 (舍孝码去)
综没慎漏上: a = -1 或 a = 2
a^2-a+1=3
a^2-a-2=0
(a-2)(a+1)=0
a=2或-1
a^2-a+1=a
a^2-2a+1=0
(a-1)^2=0
a=1 (舍去)
综手肆饥上, a的值毕返雹哗可取-1,2