∫abⅆ⁡xn⁢∫axnⅆ⁡xn-1⁢⋯⁢∫ax2ⅆ⁡x1⁢∫ax1f⁡(x)⁢ⅆ⁡x=1n!⁢∫ab(b-x)n⁢f⁡(x)⁢ⅆ⁡x.