Question 678242
{{{ax+y=c}}} 

{{{x-by=d}}}

first write it in slope-intercept form

{{{y=-ax+c}}} .......slope is {{{m=-a}}}

{{{-by=-x+d}}}

{{{y=((-1)/(-b))(x+d)}}}

{{{y=(1/b)(x+d)}}}.......slope is {{{m[1]=1/b}}}



if a line is perpendicular to the other line , then slopes are negative reciprocals: {{{m=-(1/m[1])}}}

so, {{{-a=-(1/(1/b))}}}

 {{{-a=-(b/1)}}}

{{{-a=-b}}}

and

{{{b=a}}}