\(1/2 + 1/6\\ =2/3\)
\(1/2 + 1/6 + 1/12\\ =2/3 + 1/12\\ =3/4\)
\(\therefore 1/2 + 1/6 +...+\dfrac{1}{n^2+n} = \dfrac{n}{n+1}\)
