Find the point on the line which is closest to the point .
i know you have to find the distance and then the derivative of that but i got stuck when solving for d...
Actually, you don't need calculus for this question. You need to be cognizant of this basic fact.
The shortest line between a line ($\displaystyle l_1$) and a point (P) not on the line is the perpendicular line connecting $\displaystyle l_1$ and P.
So what you do is find the equation of the line perpendicular to the given line that goes through the point (-5,4), find where it intersects the original line and then use the length of a line formula.
Sketch the graph so you have a visual idea of what is going on.