The given line is written in the form $\displaystyle{y}={m}{x}+{b}\usepackage{cmbright}\Huge\$ . Since $\displaystyle{m}={5}\usepackage{cmbright}\Huge\$ , the slope is 5. The slope of any perpendicular line would be the negative reciprocal of this slope. Therefore, its slope would be $\displaystyle-\frac{{1}}{{5}}\usepackage{cmbright}\Huge\$ . So it must have an equation in the form $\displaystyle{y}=-\frac{{1}}{{5}}{x}+{b}\usepackage{cmbright}\Huge\$ . The given equation has this form.