Incorrect. Substitute $\displaystyle-{1}\usepackage{cmbright}\Huge\$ for x in the function to get $\displaystyle{a}{\left(-{1}\right)}={2}{{\left(-{1}\right)}}^{{3}}+{5}\usepackage{cmbright}\Huge\$ and simplify the expression to find $\displaystyle{a}{\left(-{1}\right)}\usepackage{cmbright}\Huge\$ .