Ayuda, por favor?

SOLUCIÓNHola!

: DLo haremos mediante sumatorias, "E" podemos expresarla como : <img src="https://tex.z-dn.net/?f=E%20%3D%20%5Cdfrac%7B1%7D%7B2%5Ctimes6%7D%2B%20%5Cdfrac%7B1%7D%7B4%5Ctimes9%7D%2B%20%5Cdfrac%7B1%7D%7B6%5Ctimes12%7D%2B%20%5Cdfrac%7B1%7D%7B8%5Ctimes15%7D%2B...%5C%5C%5C%5C%5C%5CE%20%3D%20%5Cdfrac%7B1%7D%7B12%7D%2B%5Cdfrac%7B1%7D%7B36%7D%2B%5Cdfrac%7B1%7D%7B72%7D%2B%5Cdfrac%7B1%7D%7B120%7D%2B...%5C%5C%5C%5C%5C%5CE%20%3D%20%5Cdfrac%7B1%7D%7B6%281%29%281%2B1%29%7D%20%2B%20%5Cdfrac%7B1%7D%7B6%282%29%282%2B1%29%7D%2B%5Cdfrac%7B1%7D%7B6%283%29%283%2B1%29%7D%2B%5Cdfrac%7B1%7D%7B6%284%29%284%2B1%29%7D%2B...%5C%5C%5C%5C%5C%5CMe%20%5C%3A%20piden%20%5C%3A%2020%20%5C%3A%20sumandos%5C%3A%28L%5C%27imite%20%5C%3A%20Superior%29" /> <img src="https://tex.z-dn.net/?f=%5Csum_%7Bi%3D1%7D%5E%7B20%7D%5Cdfrac%7B1%7D%7B6i%28i%2B1%29%7D%20%3D%20%5Cdfrac%7B1%7D%7B6%7D-%5Cdfrac%7B1%7D%7B6%2820%2B1%29%7D%20%3D%20%5Cboldsymbol%7B%5Cdfrac%7B10%7D%7B63%7D%7D" />Rpta.

Alternativa A.