Question 1014701
Find the slope of line AC, and determine the slope for a line perpendicular to it.

Use point slope form of equation to make the equation of line with that slope and containing B(2,3).








AC has slope  {{{(4-1)/(-1)=-3}}}.
Slope needed will be {{{1/3}}} for the perpendicular line containing B.
{{{y-3=(1/3)(x-2)}}}-----your line containing the altitude through B.  Adjust to the form you want.