B = 3/99.96 – 3/96.93 – 3/93.90 – ……. – 3/7.4 – 3/4 LÀM NHANH MIK ĐAG CẦN GẤP ƯU TIÊN CTLHN CHO NG LÀM TRƯỚC NHÉ. THANKS!

$B=3(\dfrac{1}{99.96}-\dfrac{1}{96.93}-…-\dfrac{1}{4})$

$=3.\dfrac{1}{3}(\dfrac{1}{96}-\dfrac{1}{99}+\dfrac{1}{96}-\dfrac{1}{93}+\dfrac{1}{93}-\dfrac{1}{90}+…+\dfrac{1}{4}-1)$

$=\dfrac{1}{96}-\dfrac{1}{99}+\dfrac{1}{96}-\dfrac{1}{93}+\dfrac{1}{93}-\dfrac{1}{90}+…+\dfrac{1}{4}-1$

$=\dfrac{1}{96}-\dfrac{1}{99}+\dfrac{1}{96}-1$

$=-\dfrac{1567}{1584}$