hiiiiiiiiiii...........
heres da soln.............
y/b=tan-1[(x/a) + tan-1(y/x)]
so.........
tany/b=x/a+tan-1(y/x)
so differentiating............
sec2y/b 1/b dy/dx =1/a+1/1+(y/x)2 d/dx(y/x)
(1/bsec2y/b)dy/dx =1/a + 1/1+(y/x)^2 [y+xdy/dx)
(1/bsec2y/b)dy/dx-1/1+(y/x)^2(xdy/dx)=1/a +y/1+(y/x)2
dy/dx[(1/bsec2y/b)-x/1+(y/x)2]=1/a +y/1+(y/x)2
so therefore............
dy/dx=1/a +y/1+(y/x)2 /[(1/bsec2y/b)-x/1+(y/x)2]
hope u got it........
nice problem........