Bài 1: B= 2/8.6/15.12/24…..156/195 Bài 2: x-2/3.x=-3/4 Giúp e với ah! Cảm ơn mn nhiều:)) 13/10/2021 Bởi Remi Bài 1: B= 2/8.6/15.12/24…..156/195 Bài 2: x-2/3.x=-3/4 Giúp e với ah! Cảm ơn mn nhiều:))
Đáp án: $1)B=\dfrac{6}{2730}\\2)x=\dfrac{-1}{4}$ Giải thích các bước giải: $1)B=\dfrac{2}{8}.\dfrac{6}{15}.\dfrac{12}{24}…\dfrac{156}{195}\\=\dfrac{1.2}{2.4}.\dfrac{2.3}{3.5}.\dfrac{3.4}{4.6}…\dfrac{12.13}{13.15}\\=\dfrac{1.2.3.4…12}{2.3.4…13}.\dfrac{2.3.4…13}{4.5.6…15}\\=\dfrac{1}{13}.\dfrac{2.3}{14.15}\\=\dfrac{6}{2730}\\2)x-\dfrac{2}{3}x=\dfrac{-3}{4}\\\Leftrightarrow \left ( 1-\dfrac{2}{3} \right )x=\dfrac{-3}{4}\\\Leftrightarrow \left (\dfrac{3}{3}-\dfrac{2}{3} \right )x=\dfrac{-3}{4}\\\Leftrightarrow \dfrac{1}{3}x=\dfrac{-3}{4}\\\Leftrightarrow x=\dfrac{-1}{4}$ Bình luận
Đáp án:
$1)
B=\dfrac{6}{2730}\\
2)
x=\dfrac{-1}{4}$
Giải thích các bước giải:
$1)
B=\dfrac{2}{8}.\dfrac{6}{15}.\dfrac{12}{24}…\dfrac{156}{195}\\
=\dfrac{1.2}{2.4}.\dfrac{2.3}{3.5}.\dfrac{3.4}{4.6}…\dfrac{12.13}{13.15}\\
=\dfrac{1.2.3.4…12}{2.3.4…13}.\dfrac{2.3.4…13}{4.5.6…15}\\
=\dfrac{1}{13}.\dfrac{2.3}{14.15}\\
=\dfrac{6}{2730}\\
2)
x-\dfrac{2}{3}x=\dfrac{-3}{4}\\
\Leftrightarrow \left ( 1-\dfrac{2}{3} \right )x=\dfrac{-3}{4}\\
\Leftrightarrow \left (\dfrac{3}{3}-\dfrac{2}{3} \right )x=\dfrac{-3}{4}\\
\Leftrightarrow \dfrac{1}{3}x=\dfrac{-3}{4}\\
\Leftrightarrow x=\dfrac{-1}{4}$