Answer:
y = -x + 1
Explanation:
Any point on an angle bisector has equal distance to both sides
Bisector line slope = rise/run = -1 (rise=run and moves from left to right)
equation: y = mx + b
y = -x+b
pass (2.-1)
-1 = -2 + b B = 1
y = -x+1
check: (y- -1)/(x-2) = -1
y+1 = -x+2
y = -x + 1