Which of the following equations represents the line that passes throught the points (2, -6) and (-4,3)?

First, find the slope of the line that goes through the 2 given points, which you should know how to do.  Call it m.  Then a perpendicular line must have a slope of -1/m.  The slope-intercept form of the equation you seek is

y = (-1/m)x + b,

where b is any real number.  Examine the list of choices, and pick any that have a slope of -1/m.

check above link.

graphically?   well, you graph them both, the solutions is where they both intersect each other, since there are two solutions, meaning they will meet twice, or namely the linear will run into the quadratic curve twice, and where they meet, those x,y coordinates are the solutions to the system.