The slope of a perpendicular line is the negative reciprocal of the normal slope. For example, 3/7 would become -7/3.
Because the slope of this line is 1/5, the slope of a line that is perpendicular to it is -5.
Now, to find the equation of the line, we need to find the y intercept. Since the line passes through (0,0), that is the y intercept. Now, we can make the equation of the line.
y = -5x