Correct. Using a common denominator of $\displaystyle{\left({a}\right)}{\left({b}\right)}{\left({a}-{1}\right)}\usepackage{cmbright}\Huge\$ or $\displaystyle{{a}}^{{2}}{b}-{a}{b}\usepackage{cmbright}\Huge\$ , you find that $\displaystyle\frac{{{4}{a}}}{{{a}{b}-{b}}}-\frac{{3}}{{{a}{b}}}=\frac{{{4}{{a}}^{{2}}-{3}{a}+{3}}}{{{{a}}^{{2}}{b}-{a}{b}}}\usepackage{cmbright}\Huge\$ .