The function $\displaystyle{\left\lbrace{\left(-{1},{2}\right)},{\left({9},-{1}\right)},{\left(-{8},{5}\right)},{\left({2},-{8}\right)},{\left(?,{9}\right)}\right\rbrace}\usepackage{cmbright}\Huge\$ has the same set for its domain and range.

Find the missing value from the function. The missing value is _____.