Differentiating both sides wrt to x

2x+x dy/dx +y +2y dy/dx =0

(2x+y) + dy/dx(x+2y)=0

dy/dx = (-2x-y)/(x+2y)..............(1)

Now again differentiating dy/dx wrt x

we get [3xdy/dx -3y]/ (x=2y)^2

put the value of dy/dx from (1)

u get  -6()/ (x=2y)^3

put =a

u get  -6a/(x+2y)^3

Put the value in LHS u get Rhs