Determine for which values of m the function $\displaystyle \phi(x) = e^{mx}$ is a solution to the given equations:

(a) $\displaystyle \frac{d^2y}{dx^2} + 6\frac{dy}{dx} + 5y = 0$

(b) $\displaystyle \frac{d^3y}{dx^3} + 3\frac{d^2y}{dx^2} + 2\frac{dy}{dx} = 0$