already asked it seems : http://targetiit.com/iit_jee_forum/posts/a_p_g_p_h_p_1315.html
b2q2=acpr ...(1)
2b=a+c ........(2)
2/q=(p+r)/pr ......(3)
substitute b and q from (2) and (3) and put it in (1)
(a+c)2/4 * 4p2r2/(p+r)2=acpr
...
..
or
.
.
(p+r)2/pr=(a+c)2/ac
or p/r+r/p=a/c+c/a