集合A={y|y=x^2+2x+4,x∈R},B={y|y=ax^2-2x+4a,x∈R},且A是B的子集,求实数a的取

A是B的子集
x^2+2x+4=ax^2-2x+4a有解
(a-1)x^2-4x+4a-4=0有解≤
△=16-4(4a-4)(a-1)=16(1-(a-1)^2)≥0
(a-1)^2≤1
0≤a≤2