a, a+d, a+2d are in A.P

but in this qstn. it doesn''t matter.

Just apply the simple and sober Pythogorus formula on these sides of right triangle.

a² + (a+d)² = (a + 2d)²

a²  +  a² + d²  +2ad = a²  + 4d² + 4ad

           a² + d²  - 2ad = 4d² 

                    (a - d)²  =  4d²

                     a - d =  +-2d

Case 1.    a - d = 2d

                  a = 3d

                  a/d = 3

Case 2.   a-d = -2d

                a= - d

                  or

               d = -a

but given that d > 0

thus, answer is a/d = 3

Plz approve!!!!!!!!!!!

a^2-2ad+d^2=4^2.so a-d holl squre is eqal to +- 2d.but d>0. so a/d=3.