The slope of this line is 2, but it does not go through the point $\displaystyle{\left({1},{4}\right)}\usepackage{cmbright}\Huge\$ since when $\displaystyle{y}={4},{y}-{1}={3}\usepackage{cmbright}\Huge\$ and when $\displaystyle{x}={1},{2}{\left({x}-{4}\right)}={2}{\left(-{3}\right)}=-{6},\usepackage{cmbright}\Huge\$ so $\displaystyle{y}-{1}\ne{2}{\left({x}-{4}\right)}\usepackage{cmbright}\Huge\$ when $\displaystyle{\left({x},{y}\right)}={\left({1},{4}\right)}.\usepackage{cmbright}\Huge\$