[tex]( \frac{5}{6} - \frac{1}{16} t {}^{9} ) {}^{2} = \\ ( \frac{5}{6} ) {}^{2} - 2 \times \frac{5}{6} - \frac{1}{16} t {}^{9} + ( \frac{1}{16} {t}^{9} ) { }^{2} = \\ \frac{1}{256} {t}^{18} - \frac{5}{48} {t}^{9} + \frac{25}{36} [/tex]