He guys,

I have some questions about change of variables

I have (d^2y/dx^2)*x+x=0 and want to use the substitution z=x^2

so dy/dx=(dy/dz)*(dz/dx)=2x*(dy/dx)

But is this correct (d^2y/dx^2)=4(x^2)*(d^2y/dx^2)

My second question is, how to make the substitution z=yx in the same equation?

thanks for the help