Question 965485
<pre>
Those choices all pass through (2,2) so substituing that does no good.

We have to know two things:

1. y = mx+b.  when you see y = &#8591;x+&#8591; or y= &#8591;x-&#8591; where there are numbers in 
those boxes that the number in the first box is always the slope.

2. If one line has the slope {{{A/B}}} then a line perpendicular
to it has the slope {{{-B/A}}}.  "We flip it and change its sign" 
<font size=1>
[That's because {{{slope=rise/(run)}}}: 
a. We flip it because the 'rise' on one line becomes a 'run' on a
line perpendicular to it and vece-versa.
and 
b. We change the sign because if a line goes uphill to the right 
it has a positive slope. A line perpendicular to it goes downhill 
to the right and has a negative slope.]</font> 

So we look at {{{y = expr(1/2)x +5}}} and see that its slope is {{{1/2}}},
So we flip it and change the sign and get {{{-2/1}}} which simplifies
to {{{-2}}}.  Then we look through the list of choices and find the one
that has a {{{-2}}} as a coefficient of x.  Then we see that the only choice
is D.

Edwin</pre>