First find the slope of the line, which uses the formula:
$${\frac{\left({\mathtt{y2}}{\mathtt{\,-\,}}{\mathtt{y1}}\right)}{\left({\mathtt{x2}}{\mathtt{\,-\,}}{\mathtt{x1}}\right)}}$$
= $${\frac{\left({\mathtt{1}}{\mathtt{\,-\,}}{\mathtt{4}}\right)}{\left({\mathtt{4}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}\right)}}$$
= -3/6
=-1/2
Then plug in a point and the slope, $${\mathtt{m}}$$, into the point-slope formula:
$$\left({\mathtt{y}}{\mathtt{\,-\,}}{\mathtt{y1}}\right) = {m}{\left({\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{x1}}\right)}$$
$$\left({\mathtt{y}}{\mathtt{\,-\,}}{\mathtt{4}}\right) = {\mathtt{\,-\,}}\left({\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}\left({\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}\right)\right)$$
Move the -4 to the right side:
$${\mathtt{y}} = {\mathtt{\,-\,}}{\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{4}}$$
Simplify:
$${\mathtt{y}} = {\mathtt{\,-\,}}{\frac{{\mathtt{1}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}{\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3}}$$
.