Đáp án: a) $\frac{-3}{20}$
b) \(\left[ \begin{array}{l}x=0\\x = \frac{1}{7} \end{array} \right.\)
c) $\frac{-5}{27}$
Giải thích các bước giải:
a) $\frac{11}{12}$ - ( $\frac{2}{5}$ + x ) =$\frac{2}{3}$
$\frac{11}{12}$ - $\frac{2}{5}$ - x =$\frac{2}{3}$
$\frac{31}{60}$ - x = $\frac{2}{3}$
⇒ x = $\frac{-3}{20}$
b) 2x.( x - $\frac{1}{7}$ ) = 0
⇒ \(\left[ \begin{array}{l}2x=0\\x - \frac{1}{7}=0\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x=0\\x = \frac{1}{7} \end{array} \right.\)
c) $\frac{3}{4}$ + $\frac{1}{4}$ : x = $\frac{2}{5}$
$\frac{1}{4}$ : x = $\frac{2}{5}$ - $\frac{3}{4}$
$\frac{1}{4}$ : x = $\frac{-7}{20}$
⇒ x = $\frac{1}{4}$ : $\frac{-7}{20}$
= $\frac{-5}{27}$
@Nguyên giẻ rách
Xin hay nhất nhaaaaa~
