sturm-liouville differential equations

Question

I need method to find the values of $\lambda$

$$1.-y''+x^2 y=\lambda y$$ $$2. -y''+|x| y=\lambda y$$ $$ 3. -y''+(x^2 +x^4) y=\lambda y$$

with initial condition $y(0)=1,y'(0)=0$