Question 1057013
Horizontal means that {{{-A/B=0}}}, and {{{B<>0}}}.  This means by conclusion that {{{A=0}}}.


Now you have {{{By+C=0}}}.


Equation must include point (-3,-1).
No restrictions on x values.



{{{B*(-1)+C=0}}}

{{{-B+C=0}}}

{{{C=B}}}



Try working through slope-intercept form, instead, and you could make an easier formed equation, and then turn that result into standard form.
(Note that Ax+By+C=0 is standard form, and not general form).