Let's convert the equation in point-slope form to slope-intercept form.
y - 4 = -(x - 6)
Multiply everything out.
y - 4 = -x + 6
Add 4 to both sides.
y = -x + 10
To be perpendicular, the slope of the new has to be the reciprocal of the other line. To slope in this equation is -1/1. To get the reciprocal, flip the numerator and denominator and change the sign too.
-1/1 becomes 1/-1, and changes to 1/+1, or 1.
y = x + b
Input the coordinate point and solve for b.
-2 = -2 + b
Add 2 to both sides.
0 = b
y = x
