Question

B=\(\dfrac{1}{6.10}\)+ \(\dfrac{1}{10.14}\)+. . . + \(\dfrac{1}{402.406}\)

Các bạn giúp mình nha ! Dấu . là nhân

Answer 1

\(B=\dfrac{1}{6.10}+\dfrac{1}{10.14}+...+\dfrac{1}{402.406}\\ 4B=\dfrac{4}{6.10}+\dfrac{4}{10.14}+...+\dfrac{4}{402.406}\\ 4B=\dfrac{1}{6}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{14}+...+\dfrac{1}{402}-\dfrac{1}{406}\\ 4B=\dfrac{1}{6}-\dfrac{1}{406}=\dfrac{100}{609}\\B=\dfrac{\dfrac{100}{609}}{4}=\dfrac{25}{609} \)

Answer 2

\(B=\dfrac{1}{6}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{14}+...+\dfrac{ 1}{402}-\dfrac{1}{406}\)

\(=\dfrac{1}{6}-\dfrac{1}{406}=\dfrac{100}{609}.\)

Answer 3

Các bn giúp mk nha mk đg cần gấp

Answer 4

hoàng ngọc anh làm sai rồi