$\displaystyle\frac{{{b}-{1}}}{{{\left({b}+{2}\right)}{\left({b}-{1}\right)}}}\usepackage{cmbright}\Huge\$ , domain all $\displaystyle{b}\usepackage{cmbright}\Huge\$ , $\displaystyle{b}\ne{1}\usepackage{cmbright}\Huge\$ , 2, 3, and -1