y*x^2+y=ax^2+8x+b
(a-y)x^2+8x+b-y=0
x有解,该方程满足：64-4(a-y)(b-y)>=0
由值域｛y∣1≤y≤9｝,当y=1和9时,上式的等号成立.即
64-4(a-1)(b-1)=0;64-4(a-9)(b-9)=0
可得：a=5,b=5