Câu 2: Trang 31 sách toán VNEN lớp 6 tập 2
Tìm x, biết:
a) $x\;-\;\frac{1}{4} = \frac{-3}{8}\times\frac{2}{5}$.
b) $\frac{x}{126} = \frac{-7}{24}\times\frac{-6}{11}$
Bài Làm:
a) $x\;-\;\frac{1}{4} = \frac{-3}{8}\times\frac{2}{5}$.
$\Leftrightarrow x\;-\;\frac{1}{4} = \frac{-6}{40}$
$\Leftrightarrow x\;-\;\frac{1}{4} = \frac{-3}{20}$
$\Leftrightarrow x = \frac{-3}{20}\;+\;\frac{1}{4}$
$\Leftrightarrow x = \frac{-3}{20}\;+\;\frac{5}{20}$
$\Leftrightarrow x = \frac{2}{20}$
$\Leftrightarrow x = \frac{1}{10}$
b) $\frac{x}{126} = \frac{-7}{24}\times\frac{-6}{11}$
$\Leftrightarrow \frac{x}{126} = \frac{42}{264}$
$\Leftrightarrow \frac{x}{126} = \frac{7}{44}$
$\Leftrightarrow x = 126\times \frac{7}{44}$
$\Leftrightarrow x = \frac{126\times 7}{44}$
$\Leftrightarrow x = \frac{441}{22}$