解：?$(1)$?如圖所示?$ $?
?$(2)$?觀察數(shù)據(jù)，選擇一次函數(shù)模型?$y = kx + b$?
?$ $?取?$(23，$??$156)$?和?$(24，$??$163)$?代入?$y = kx + b$?
得?$\begin {cases}23k + b=156\\24k + b=163\end {cases}，$?解得?$\begin {cases}{k = 7}\\{b =-5}\end {cases}$?
∴函數(shù)表達(dá)式為?$y = 7x-5$?
?$ (3)$?當(dāng)?$x = 25.8$?時(shí)，代入得?$ y=7×25.8-5=175.6(\mathrm {cm})$?
