f = R/2

 

I have taken upper part + ve and lower part - ve

using mirror formula

1/f = 1/v + 1/u

putting value we get

 

1/-f = 1/v - 1/u

 

solving we get v = uR/(R-2u)

So xd = u + v

bus as in diagram ray after refraction will cause shift and image formed at G

 

shift = (u+v)(1  -  1/x)

 

now subtract shift from xd u will get it