Given the vectors a= (-1,9) and b= (4,2) explain the difference between a-b and b-a. Thank you for your help! :)

a-b = -(b-a)

so, they are vectors of the same magnitude, but in opposite directions.

as you know, a+b is like the diagonal of a parallelogram with a and b as two sides.

a-b is the other diagonal.