解：?$(1)$?∵拋物線?$y=ax2+bx+2$?經(jīng)過(guò)
點(diǎn)?$A(-1$?，?$0)$?，?$B(4$?，?$0)$?
∴?$\begin {cases}{a-b+2=0}\\{16a+4b+2=0}\end {cases}$?，解得?$\begin {cases}{a=-\frac 12}\\{b=\frac {3}{2}}\end {cases}$?
∴拋物線的解析式為?$y=-\frac 12x^2+\frac {3}{2}x+2$?
?$(2)$?點(diǎn)?$D(1$?，?$3)$?或?$(2$?，?$3)$?或?$(5$?，?$-3)$?
