2a²+a+1=2(a+1/4)^2+7/8>0
2a²-2a+3=2(a-1/2)^2+5/2>0
函数f(x)在R上是偶函数,在区间(-∞,0)上递增,所以在(0,∞)上递减
2a²+a+1>2a²-2a+3
a>2/3