$$y＝f（x|{\nu }_1，{\nu }_2）＝\frac{\Gamma ［\frac{（{\nu }_1+{\nu }_2）}{2}］}{\Gamma （\frac{{\nu }_1}{2}）\Gamma （\frac{{\nu }_2}{2}）}{（\frac{{\nu }_1}{{\nu }_2}）}^{\frac{{\nu }_1}{2}}\frac{x^{\frac{{\nu }_1-2}{2}}}{{［1+（\frac{{\nu }_1}{{\nu }_2}）x］}^{\frac{{\nu }_1+{\nu }_2}{2}}}$$