First, find the slope of the given line. We can do this by translating the equation into slope intercept form (y=mx+b).
The slope of a line perpendicular to the given line will be the "negative reciprocal" of the given line; thus
Use this slope along with the given point (2, 1) and substitute them into the following point-slope form of a linear equation.
Now, you can rearrange the above equation into other forms as required.