Two lines are perpendicular if their slope m and m' satisfy the equation
The slope of the given line is 4, because the line is written in the slope-intercept y=mx+q, where m is the slope.
So, the perpendicular slope is
So, we want a line with slope -1/4 and passing through (-1,3). We can use the formula
for the line passing trough (a,b) with slope m: