a+2+1=0
a=-3
-3x^2+2x+1=0
-1 1
3 1
(-x+1)(3x+1)=0
x=1 x=-1/3
A={-1/3,1}
(2)A=｛x属于R/ax^2+2x+1=0｝
b²-4ac=4-4a=0
a=1
B={1}