1: \(=\left(\dfrac{1}{2}:\dfrac{-2}{3}\right)\cdot\left(a^m:a^2\right)\cdot\left(b^n:b\right)\cdot\left(c^2:c\right)\)
\(=\dfrac{-3}{4}a^{m-2}b^{n-1}c\)
2: \(=\dfrac{2}{7}\left(x-2y\right)^{2m+1}\cdot\dfrac{-14}{5\left(2y-x\right)^{2m-1}}\)
\(=\dfrac{-4}{5}\cdot\dfrac{-\left(2y-x\right)^{2m+1}}{\left(2y-x\right)^{2m-1}}=\dfrac{4}{5}\cdot\left(2y-x\right)^2\)