In Problems $31-36$ use the substitution $x=e^t$ to transform the given Cauchy$-$Euler equation to a differential equation with constant coefficients. Solve the original equation by solving the new equation using the procedures in Sections $4\mathrm{.}3-4\mathrm{.}5.$

$31.x^2{y}^{\text{'}\text{'}}+9x{y}^{\text{'}}-20y=0$

$32.x^2{y}^{\text{'}\text{'}}-9x{y}^{\text{'}}+25y=0$

$33.x^2{y}^{\text{'}\text{'}}+10x{y}^{\text{'}}+8y=x^2$

$34.x^2{y}^{\text{'}\text{'}}-4x{y}^{\text{'}}+6y=ln{x}^2$

$35.x^2{y}^{\text{'}\text{'}}-3x{y}^{\text{'}}+13y=4+3x$