If `a=(2,1,-1), b=(1,-1,0),c=(5,-1,1)`, then what is the unit vector parallel to `a+b-c` in the opposite direction?

if a = (2,1,-1) , b= (1,-1,0) , c = (5,-1,1) then unit vector parallel to a + b -c but opposite direction

If vec(a)=(2,1,-1), vec(b)=(1,-1,0), vec(c)=(5, -1,1) , then what is the unit vector parallel to vec(a)+vec(b)-vec(c) in the opposite direction ?

If vec(a)= (2, 1, -1), vec(b) = (1, -1, 0), c= (5, -1, 1) , then what is the unit vector parallel to vec(a) +vec(b)- vec(c ) in the oppoiste direction?

If bar(a)=(2,1,-1),bar(b)=(1,-1,0),bar(c)=(5,-1,1) then the unit vector parallel to bar(a)+bar(b)-bar(c) but in the opposite direction is

If bar(a)=(2,1,-1),bar(b)=(1,-1,0),bar(c)=(5,-1,1) then the unit vector parallel to bar(a)+bar(b)-bar(c) but in the opposite direction is

If bar(a)=(2,1,-1),bar(b)=(1,-1,0),bar(c)=(5,-1,1) then the unit vector parallel to bar(a)+bar(b)-bar(c) but in the opposite direction is

If bar(a)=(2,1,-1),bar(b)=(1,-1,0),bar(c)=(5,-1,1) then the unit vector parallel to bar(a)+bar(b)-bar(c) , but in the opposite direction is

If bara=(2,1,-1),bar(b)=(1,-1,0),bar(c)=(5,-1,1) then the unit vector parallel to bar(a)+bar(b)-bar(c) ,but in the opposite direction is