设函数为y=ax^2+bx+c
16a+4b+c=3...(1)
a-b+c=-8...(2)
4a+2b+c=1...(3)
(1)-(2) 得 15a+5b=11...(4)
(3)-(2) 得 3a+3b=9 =>a+b=3...(5)
(4)-(5)*5 得 10a=-4 =>a=-2/5
将a=-2/5代入（5）得-2/5+b=3 =>b=3+2/5=17/5
将结果代入（2）得 -2/5-17/5+c=-8 =》c=19/5-8=-21/5
解析式为y=-2/5x^2+17/5x-21/5