Given $\displaystyle{a}{\left({x}\right)}={2}{{x}}^{{3}}+{5}\usepackage{cmbright}\Huge\$ , find $\displaystyle{a}{\left(-{1}\right)}\usepackage{cmbright}\Huge\$ .

$\displaystyle{a}{\left(-{1}\right)}=\usepackage{cmbright}\Huge\$ _____