Question 1106045
<pre>
Just use the point slope formula:

y - y<sub>1</sub> = m(x - x<sub>1</sub>)
where (x<sub>1</sub>,y<sub>1</sub>) = (1,2)

(a) using m = 3:

{{{y-2=3(x-1)}}}
{{{y-2=3x-3}}}
{{{y=3x-1}}}

That's this red line:

{{{drawing(400,400,-10,10,-10,10, graph(400,400,-10,10,-10,10),
blue(line(-11,-34, 11,32)))}}}

(a) using m = {{{1/3))):

{{{y-2=expr(1/3)(x-1)}}}
Multiply both sides by 3
{{{3y-6=x-1}}}
{{{3y=x+5}}}
{{{y=expr(-1/3)x+5/3}}}

That's this green line:

{{{drawing(400,400,-10,10,-10,10, graph(400,400,-10,10,-10,10),
blue(line(-11,-34, 11,32)),
green(line(11,-2,-13,6))


)}}}

They're perpendicular because their slopes are negative reciprocals,
which is the same as saying that when you multiply their slopes
together, you get -1.  {{{(3^""^"")(-1/3)=-1}}}
 
Edwin</pre>