y = \frac{| \binom{a_{1}}{a_{2}} \binom{c_{1}}{c_{2}} |}{| \binom{a_{1}}{a_{2}} \binom{b_{1}}{b_{2}} |}

${y = \frac {\left|{a_1 \atop a_2} \, {c_1 \atop c_2} \right|} { \left|{a_1 \atop a_2} \, {b_1 \atop b_2} \right|}}$

Error