First thing, a line connecting the two points does NOT pass through the origin....
so use the distance formula TWICE once for the distance from -4,5 to 0,0
and once for the distance from 5,-4 to 0,0 then add them together
fiirst one d^2 = (-4)^2 + 5^2
d = sqrt 41
second one d^2 = 5^2 + -4^2
d = sqrt41
d = 2 sqrt 41 from point a to origin then to point b