Answer:
The value is always zero .
Step-by-step explanation:
If both have different values
a = 10, b = 20
As
xp = xp+yp so
xp = 30
yp =20
As
yp = xp-yp
so xp=30
yp=10
Now
xp = xp-yp = 20
so we can conclude that both a and b have been interchanged.
if both direct to same object
then
xp = xp+yp
so xp = 40
yp =40
Now
yp = xp-yp
so xp=0
yp=0
and
xp = xp-yp = 20