The slope of the given line is ∆y/∆x = (4-6)/(5-1) = -2/4 = -1/2. The slope of the desired (perpendicular) line is the negative reciprocal of this, -1/(-1/2) = 2.
The point-slope form of the equation for a line with slope m through point (h, k) is
... y - k = m(x - h)
For slope 2 and the given point, your equation can be
... y + 6 = 2(x + 2)
