Ta có: \(\dfrac{2}{5}-\dfrac{4a+13}{10a-5}\)
\(=\dfrac{2}{5}-\dfrac{4a+13}{5\left(2a-1\right)}\)
\(=\dfrac{2\left(2a-1\right)}{5\left(2a-1\right)}-\dfrac{4a+13}{5\left(2a-1\right)}\)
\(=\dfrac{4a-2-4a-13}{5\left(2a-1\right)}\)
\(=\dfrac{-15}{5\left(2a-1\right)}\)
\(=\dfrac{-3}{2a-1}\)