What Is the Characteristic Equation of the Differential Equation $9 \frac{d^{2} y}{d x^{2}}+2 \frac{d y}{d x}-27 y=0$

What is the characteristic equation of the differential equation $9 \frac{d^{2} y}{d x^{2}}+2 \frac{d y}{d x}-27 y=0$ ?