ok in this problem im supposed to use the substitution x = e^t to transform the given Cauchy-Euler equation to a differential equation with constant coefficients.

x^2y'' +9xy' -20y=0

im not sure how to start this problem

maybe dy/dx= (dy/dt)(dt/dx) = (dy/dt)e^t

so then could i say d2y/dx^2 = (e^t)d2y/dt^2<---- ?

maybe then i could substitute back into the equation? i dunnno..

any help would be appreciated thanks in advance.