[tex]\displaystyle (\frac{5}{6}-\frac{1}8}t^6)^2=(\frac{5}{6})^2-2*\frac{5}{6}*\frac{1}{8}t^6+(\frac{1}{8}t^6)^2=\frac{1}{64}t^1^2-\frac{5}{24}t^6+\frac{25}{36}[/tex]