f(1)=a+b+c=-11.1
f(x)'=3ax^2+2bx+c
由x=正负1时取得极值得
f(1)'=3a+2b+c=0.2
f(-1)'=3a-2b+c=0.3
又由1,2,3联立得a=5.5,b=0,c=-16.5