B=1/20+1/42+1/56+1/72+1/90+1/110+1/132 giúp 10/11/2021 Bởi Claire B=1/20+1/42+1/56+1/72+1/90+1/110+1/132 giúp
Giải thích các bước giải: $B = \dfrac{1}{30} + \dfrac{1}{42} + \dfrac{1}{56} + \dfrac{1}{72} + \dfrac{1}{90} + \dfrac{1}{110} + \dfrac{1}{132}$ $= \dfrac{1}{5.6} + \dfrac{1}{6.7} + \dfrac{1}{7.8} + \dfrac{1}{8.9} + \dfrac{1}{9.10} + \dfrac{1}{10.11} + \dfrac{1}{11.12}$ $= \dfrac{1}{5} – \dfrac{1}{6} + \dfrac{1}{6} – \dfrac{1}{7} + \dfrac{1}{7} – \dfrac{1}{8} + \dfrac{1}{8} – \dfrac{1}{9} + \dfrac{1}{9} – \dfrac{1}{10} + \dfrac{1}{10} – \dfrac{1}{11} + \dfrac{1}{11} – \dfrac{1}{12}$ $= \dfrac{1}{5} – \dfrac{1}{12}$ $= \dfrac{7}{60}$ Bình luận
$B = 1/20 + 1/42 + 1/56 + 1/72 + 1/90 + 1/110 + 1/132$ $= 1/4.5 + 1/6.7 + 1/7.8 + 1/8.9 + 1/9.10 + 1/10.11 + 1/11.12$ $= 1/20 + 1/6 – 1/7 + 1/7 – 1/8 + 1/8 – 1/9 + 1/9 – 1/10 + 1/10 – 1/11 + 1/11 – 1/12$ $= 1/20 + 1/6 – 1/12$ $= 1/20 + (2/12 – 1/12)$ $= 1/20 + 1/12$ $= 3/60 + 5/60$ $= 8/60 = 2/15$ Vậy $B = 2/15$ HỌC TỐT! Bình luận
Giải thích các bước giải:
$B = \dfrac{1}{30} + \dfrac{1}{42} + \dfrac{1}{56} + \dfrac{1}{72} + \dfrac{1}{90} + \dfrac{1}{110} + \dfrac{1}{132}$
$= \dfrac{1}{5.6} + \dfrac{1}{6.7} + \dfrac{1}{7.8} + \dfrac{1}{8.9} + \dfrac{1}{9.10} + \dfrac{1}{10.11} + \dfrac{1}{11.12}$
$= \dfrac{1}{5} – \dfrac{1}{6} + \dfrac{1}{6} – \dfrac{1}{7} + \dfrac{1}{7} – \dfrac{1}{8} + \dfrac{1}{8} – \dfrac{1}{9} + \dfrac{1}{9} – \dfrac{1}{10} + \dfrac{1}{10} – \dfrac{1}{11} + \dfrac{1}{11} – \dfrac{1}{12}$
$= \dfrac{1}{5} – \dfrac{1}{12}$
$= \dfrac{7}{60}$
$B = 1/20 + 1/42 + 1/56 + 1/72 + 1/90 + 1/110 + 1/132$
$= 1/4.5 + 1/6.7 + 1/7.8 + 1/8.9 + 1/9.10 + 1/10.11 + 1/11.12$
$= 1/20 + 1/6 – 1/7 + 1/7 – 1/8 + 1/8 – 1/9 + 1/9 – 1/10 + 1/10 – 1/11 + 1/11 – 1/12$
$= 1/20 + 1/6 – 1/12$
$= 1/20 + (2/12 – 1/12)$
$= 1/20 + 1/12$
$= 3/60 + 5/60$
$= 8/60 = 2/15$
Vậy $B = 2/15$
HỌC TỐT!