答：抛物线与X轴交A(-1,0) B(2,0)并经过点M（0,1）则对称轴x=(-1+2)/2=1/2设f(x)=a(x-1/2)^2+k点M和点B坐标代入得：f(0)=a/4+k=1f(2)=9a/4+k=0联立上两式解得：a=-1/2,k=9/8所以：f(x)=(-1/2)(x-1/2)^2+9/8所以：f(x...