a: \(=\dfrac{-3}{4}-\dfrac{1}{36}-\dfrac{2}{9}+\dfrac{1}{3}+\dfrac{1}{15}+\dfrac{3}{5}+\dfrac{1}{57}\)
=1/57-1+1
=1/57
b: \(=\dfrac{1}{4}\left(\dfrac{4}{1\cdot5}+\dfrac{4}{5\cdot9}+...+\dfrac{4}{41\cdot45}\right)\)
\(=\dfrac{1}{4}\left(1-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{9}+...+\dfrac{1}{41}-\dfrac{1}{45}\right)\)
=1/4*44/45
=11/45