You may have known that the denominator of the function could not be equal to 0, but this does not mean that $\displaystyle{x}+{5}\usepackage{cmbright}\Huge\$ can only have positive values. If $\displaystyle{x}+{5}>{0}\usepackage{cmbright}\Huge\$ , then for this function $\displaystyle{f{{\left({x}\right)}}}>{0}\usepackage{cmbright}\Huge\$ , so the wrong domain has led you to the wrong range. If you graph the function you will find a horizontal asymptote. This fact will help you find the range.