Question 942746
y=A+B(x-8), is the perpendicular line to y=2x and  contains (5,13).


That means, {{{highlight(B=-1/2)}}}.


{{{y=A+(-1/2)(x-8)}}}
{{{A=y+(1/2)(x-8)}}}
{{{A=13+(1/2)(5-8)}}}
{{{A=13-3/2}}}
{{{A=26/2-3/2}}}
{{{highlight(A=23/2)}}}