Bạn tham khảo!
Bài 1.
$a)$ $\dfrac{2}{5}$ $+$ $|$ $\dfrac{-3}{2}$ $|$ $-$ $\dfrac{4}{3}$
$=$ $\dfrac{2}{5}$ $+$ $\dfrac{3}{2}$ $-$ $\dfrac{4}{3}$
$=$ $\dfrac{17}{30}$
$b)$ $\dfrac{8}{5}$ $.$ $\dfrac{7}{13}$ $+$ $\dfrac{8}{5}$ $.$ $\dfrac{6}{13}$ $-$ $\dfrac{3}{5}$
$=$ $\dfrac{8}{5}$ $.$ $($ $\dfrac{7}{13}$ $+$ $\dfrac{6}{13}$ $)$ $-$ $\dfrac{3}{5}$
$=$ $\dfrac{8}{5}$ $.$ $1$ $-$ $\dfrac{3}{5}$
$=$ $\dfrac{8}{5}$ $-$ $\dfrac{3}{5}$
$=$ $1$
$c)$ $($ $\dfrac{-1}{3}$ $)^{2}$ $-$ $1^{2018}$ $+$ $\dfrac{2}{9}$ $:$ $|$ $\dfrac{-4}{15}$ $|$
$=$ $\dfrac{1}{9}$ $-$ $1$ $+$ $\dfrac{2}{9}$ $:$ $\dfrac{4}{15}$
$=$ $\dfrac{1}{9}$ $-$ $1$ $+$ $\dfrac{5}{6}$
$=$ $\dfrac{-1}{18}$
$d)$ mờ quá
Bài 2.
$a)$ $\dfrac{2}{3}$ $-$ $x$ $=$ $1\dfrac{1}{6}$
$→$ $\dfrac{2}{3}$ $-$ $x$ $=$ $\dfrac{7}{6}$
$→$ $x$ $=$ $\dfrac{-1}{2}$
$b)$ $($ $\dfrac{2}{5}$ $-$ $x$ $)$ $:$ $\dfrac{3}{7}$ $=$ $\dfrac{7}{5}$
$→$ $\dfrac{2}{5}$ $-$ $x$ $=$ $\dfrac{3}{5}$
$→$ $x$ $=$ $\dfrac{-1}{5}$
$c)$ $|$ $2x$ $+$ $\dfrac{1}{3}$ $|$ $-$ $\dfrac{2}{5}$ $=$ $4$
$→$ $|$ $2x$ $+$ $\dfrac{1}{3}$ $|$ $=$ $|$ $\dfrac{22}{5}$
$→$ $2x$ $+$ $\dfrac{1}{3}$ $=$ $\dfrac{22}{5}$ hoặc $2x$ $+$ $\dfrac{1}{3}$ $=$ $\dfrac{-22}{5}$
$→$ $2x$ $=$ $\dfrac{61}{15}$ hoặc $2x$ $=$ $\dfrac{-71}{15}$
$→$ $x$ $=$ $\dfrac{61}{30}$ hoặc $x$ $=$ $\dfrac{-71}{30}$
Bài 3.
$\dfrac{x}{5}$ $=$ $\dfrac{y}{7}$ $=$ $\dfrac{z}{3}$ và $x$ $+$ $y$ $-$ $z$ $=$ $18$
Áp dụng t/c dãy tỉ số $=$ nhau ta có :
$\dfrac{x}{5}$ $=$ $\dfrac{y}{7}$ $=$ $\dfrac{z}{3}$ $=$ $\dfrac{x+y-z}{5+7-3}$ $=$ $\dfrac{18}{9}$ $=$ $2$
$→$ $\dfrac{x}{5}$ $=$ $2$ $→$ $x$ $=$ $10$
và $\dfrac{y}{7}$ $=$ $2$ $→$ $y$ $=$ $14$
và $\dfrac{z}{3}$ $=$ $2$ $→$ $z$ $=$ $6$
$FbBinhne2k88$
