$\displaystyle{9}{{c}}^{{2}}\usepackage{cmbright}\Huge\$ is a common factor, but not the GCF. Also, this is an incorrect factorization. You may have incorrectly thought that the exponents get multiplied when you multiply the variables. If you used the distributive property to multiply $\displaystyle{9}{{c}}^{{2}}{\left({5}{{c}}^{{3}}+{6}{{c}}^{{4}}\right)}\usepackage{cmbright}\Huge\$ , you would get $\displaystyle{45}{{c}}^{{5}}+{54}{{c}}^{{6}}\usepackage{cmbright}\Huge\$ , not $\displaystyle{45}{{c}}^{{6}}+{54}{{c}}^{{8}}\usepackage{cmbright}\Huge\$ .