With two points you can define a line.
So, the line parallel to s is q, which has these two points: (3,6) and (6,3)
There are different ways to get the line. For instance, this one:
y = a*x+b,
a = slope = difference_y/difference_x = (3-6)/(6-3) = -1,
y = -x + b,
Now use any point, say (3,6) to get b:
6 = -3+b-> b = 9,
line is y = -x + 9,
It checks out in the other point: (6,3) --> 3 = -6+9 = 3. Good.
Other method could be:
y-y2 = a*(x-x2), where (x2,y2) is one of the two points and a is the slope as defined before.
Hope it helps!
