The value of y = x(r -1)
Given expression is : x+y-xr
Now, on rearranging the terms of the expression we get,
x -xr + y
Now, we put it equal to zero to find the value:
x -xr + y = 0
⇒ y = xr -x (The signs changes on moving from left-hand side of the equation to the right hand side)
⇒ y = x(r -1)