Câu hỏi của Nguyễn Đa Tiến

Question

A=$\dfrac{2}{15}$ +$\dfrac{2}{35}$ +$\dfrac{2}{63}$ +...+$\dfrac{2}{575}$

Tóc Em Rối Rồi Kìa · Accepted Answer

$A=\dfrac{2}{15}+\dfrac{2}{35}+...+\dfrac{2}{575}\
=\dfrac{2}{3\cdot5}+\dfrac{2}{5\cdot7}+...+\dfrac{2}{23\cdot25}\
=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{23}-\dfrac{1}{25}\
=\dfrac{1}{3}-\dfrac{1}{25}\
=\dfrac{25}{75}-\dfrac{3}{75}\
=\dfrac{22}{75}$Câu trả lời: $A=\dfrac{2}{15}+\dfrac{2}{35}+...+\dfrac{2}{575}\
=\dfrac{2}{3\cdot5}+\dfrac{2}{5\cdot7}+...+\dfrac{2}{23\cdot25}\
=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{23}-\dfrac{1}{25}\
=\dfrac{1}{3}-\dfrac{1}{25}\
=\dfrac{25}{75}-\dfrac{3}{75}\
=\dfrac{22}{75}$

my yến · Answer

A $=$ $\dfrac{2}{15}$ $+$ $\dfrac{2}{35}$  $+$ $\dfrac{2}{63}$ $+$ . . . . . $+$ $\dfrac{2}{575}$

$=$ $\dfrac{2}{3.5}$ $+$ $\dfrac{2}{5.7}$ $+$ $\dfrac{2}{7.9}$ $+$ . . . . . $+$ $\dfrac{2}{23.25}$

$=$ $\dfrac{1}{3}$ $-$ $\dfrac{1}{5}$ $+$ $\dfrac{1}{5}$ $-$ $\dfrac{1}{7}$ $+$ $\dfrac{1}{7}$ $-$ $\dfrac{1}{9}$ $+$ . . . . . $+$ $\dfrac{1}{23}$ $-$ $\dfrac{1}{25}$

$=$ $\dfrac{1}{3}$ $-$ $\dfrac{1}{25}$

$=$ $\dfrac{22}{75}$Câu trả lời: A $=$ $\dfrac{2}{15}$ $+$ $\dfrac{2}{35}$  $+$ $\dfrac{2}{63}$ $+$ . . . . . $+$ $\dfrac{2}{575}$

$=$ $\dfrac{2}{3.5}$ $+$ $\dfrac{2}{5.7}$ $+$ $\dfrac{2}{7.9}$ $+$ . . . . . $+$ $\dfrac{2}{23.25}$

$=$ $\dfrac{1}{3}$ $-$ $\dfrac{1}{5}$ $+$ $\dfrac{1}{5}$ $-$ $\dfrac{1}{7}$ $+$ $\dfrac{1}{7}$ $-$ $\dfrac{1}{9}$ $+$ . . . . . $+$ $\dfrac{1}{23}$ $-$ $\dfrac{1}{25}$

$=$ $\dfrac{1}{3}$ $-$ $\dfrac{1}{25}$

$=$ $\dfrac{22}{75}$

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