1A:
a: \(=\dfrac{2x-1-4x+1}{5x^2y}=\dfrac{-2x}{5x^2y}=\dfrac{-2}{5xy}\)
b: \(=\dfrac{y+8}{\left(y-4\right)\left(y+4\right)}-\dfrac{2}{y\left(y+4\right)}\)
\(=\dfrac{y^2+8y-2y+8}{y\left(y-4\right)\left(y+4\right)}=\dfrac{\left(y+2\right)\left(y+4\right)}{y\left(y-4\right)\left(y+4\right)}\)
\(=\dfrac{y+2}{y\left(y-4\right)}\)
2A:
a: \(=\dfrac{x+1}{x-5}+\dfrac{x-1}{x+5}-\dfrac{2x\left(x-1\right)}{\left(x-5\right)\left(x+5\right)}\)
\(=\dfrac{x^2+6x+5+x^2-6x+5-2x^2+2x}{\left(x-5\right)\left(x+5\right)}=\dfrac{2x+10}{\left(x-5\right)\left(x+5\right)}=\dfrac{2}{x-5}\)
b: \(=\dfrac{m^4-1-m^4+4m^2-3}{m^2-1}=\dfrac{4m^2-4}{m^2-1}=4\)
