You may have correctly simplified the expression to $\displaystyle\frac{{5}}{{{2}{y}}}\cdot\frac{{{{y}}^{{2}}+{2}{y}}}{{{{y}}^{{2}}-{4}}}\usepackage{cmbright}\Huge\$ , but then incorrectly tried to "cancel" the $\displaystyle{{y}}^{{2}}\usepackage{cmbright}\Huge\$ terms. To simplify fractions you have to factor the numerators and denominators. Then regroup common factors in the same fraction and reduce to 1.