Question 949115
That perpendicular unknown line is {{{y=-(1/2)x+b}}}.


Use the point to be included in this equation solved for b 
{{{b=y+(1/2)x}}}
{{{b=2+(1/2)*1}}}
{{{b=2&1/2}}}


FOUND LINE:  {{{highlight(y=-(1/2)x+2&1/2)}}}