If LaTeX: A=\begin{bmatrix} \dfrac{1}{2}&1\\
\dfrac{1}{4} &\dfrac{1}{10}
\end{bmatrix}A = [ 1 2 1 1 4 1 10 ] and LaTeX: A^{-1}=\begin{bmatrix}
a_{1}&a_{2}\\
a_{3}&a_{4}
\end{bmatrix}A − 1 = [ a 1 a 2 a 3 a 4 ], what is the value of LaTeX: a_{2} a 2?