Let $f(x)=\displaystyle\int\frac{7x^{10}+9x^8}{(1+x^2+2x^9)^2}dx$, $x>0$, $\lim_{x\to0}f(x)=0$ and $f(1)=\dfrac{1}{4}$. If $A=\begin{bmatrix}0&0&1\\\frac{1}{4}&f'(1)&1\\\alpha^2&4&1\end{bmatrix}$ and $B=\text{adj}(\text{adj}\,A)$ be such that $|B|=81$, then $\alpha^2$ is equal to