E(x)=E(0)+\frac{\mathrm{d}E}{\mathrm{d}x}x+\frac{1}{2!}\frac{\mathrm{d}^2E}{\mathrm{d}x^2}x^2+\frac{1}{3!}\frac{\mathrm{d}^3E}{\mathrm{d}x^3}x^3+...