带入x=-2和x=-1/2
4a-2b+c=0,1/4*a-1/2*b+c=0
得到a=c,b=5/2*c
(c=0,否则原不等式不成立)
cx^2-5/2*c*x+c>0划为(x-1/2)(x-2)>0
于是,解集为{x[x2}