Problem: Find the leading order WKB approximation for the specific differential equation: $\epsilon^2 y'' = (2+x+3x^2)^2y$ with initial conditions at $y(0) = 0, y'(0)=1$ where $\epsilon$ is a small positive parameter ($0 < \epsilon \ll 1$
Solution: $\boxed{y(x) = \frac{\epsilon}{\sqrt{2(2+x+3x^2)}} \sinh[\frac{2x+\frac{1}{2}x^2+x^3}{\epsilon}]}$