Hi all, I have what should hopefully be a quick question. Given an ODE of the following form (sorry no tex) y = y(x) with y' defined as differentiation wrt (with respect to) x y'' + y' + y = 0 and I want to make a change a variables A = x/a (for some constant a) so that we define a new dependent variable as Y(A) = y(ax). I now want to rewrite the ODE with respect to Y and A. Y = Y(A) with Y* defined as differentiation wrt A I am not sure how this works out, but I know that the answer should look like 1/a^2 Y** + 1/a Y* + Y = 0 I know this isnt a hard question but I'm just not seeing it. Thanks in advance for help. EDIT: I found a way for this to work out, although it seems a bit convoluted. Input still welcome though.