Đáp án:
Giải thích các bước giải:
`C = 1/2+1/14+1/35+1/65+1/104+1/152`
$=\dfrac{2}{4}+\dfrac{2}{28}+\dfrac{2}{70}+\dfrac{2}{130}+\dfrac{2}{208}+\dfrac{2}{304}$
$=\dfrac{2}{3}\cdot(\dfrac{3}{4}+\dfrac{3}{28}+\dfrac{3}{70}+\dfrac{3}{130}+\dfrac{3}{208}+\dfrac{3}{304})$
$=\dfrac{2}{3}\cdot(\dfrac{3}{1\cdot4}+\dfrac{3}{4\cdot7}+\dfrac{3}{7\cdot10}+\dfrac{3}{10\cdot13}+\dfrac{3}{13\cdot16}+\dfrac{3}{16\cdot19})$
$=\dfrac{2}{3}\cdot(\dfrac{1}{1}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{19})$
$=\dfrac{2}{3}\cdot(1-\dfrac{1}{19})$
$=\dfrac{2}{3}\cdot\dfrac{18}{19}$
$=\dfrac{12}{19}$
