Alternatively, since we know the perpendicular slope is -2, as pointed out above, we could use point-slope form as an alternative.

Point-slope is y-y1=m(x-x1). Plugging the numeric values in place give y-(-1)=-2(x-1).

Simplified, y+1=-2x+2. Simplifying to slope-intercept form, y=-2x+1.