*Gửi tus

Trả lời:

(Như trên ảnh ạ, bài 2 tìm x, máy mik chụp hơi lỗi nhưng vẫn nhìn đc nha Tus)

*Chúc bn học tốt ^^
*Xin hn ạ :3
$#Tienmanhhoang$
$#Kẻ_Hủy_Diệt$

Bài 1.

$a)$ $\dfrac{1}{3}-\dfrac{3}{4}+\dfrac{2}{5}$

$=\dfrac{20}{60}-\dfrac{45}{60}+\dfrac{24}{60}$

$=\dfrac{20-45+24}{60}$

$=-\dfrac{1}{60}$

$b)$ $\dfrac{-1}{13}\cdot \dfrac{5}{11}+\left(\dfrac{-1}{13}\right)\cdot \dfrac{6}{11}$

$=\left(-\dfrac{1}{13}\cdot \dfrac{5}{11}\right)+\left(\left(-\dfrac{1}{13}\right)\dfrac{6}{11}\right)$

$=-\dfrac{5}{143}-\dfrac{6}{143}$

$=-\dfrac{1}{13}$

$c)$ $\left(-\dfrac{1}{3}\right)^2+\left|\dfrac{-3}{7}\right|:\dfrac{2}{7}$

$=\left(\dfrac{1}{3}\right)^2+\dfrac{3}{7}:\dfrac{2}{7}$

$=\left(\left(\dfrac{1}{3}\right)^2+\dfrac{3}{7}\right)\cdot \:7:2$

$=\dfrac{34}{9}:2$ $=\dfrac{34}{9\cdot \:2}$ $=\dfrac{34}{18}$

$=\dfrac{17}{9}$

Bài 2.

$a)$ $x-\dfrac{1}{3}=\dfrac{-5}{2}$

$x-\dfrac{1}{3}=-\dfrac{5}{2}$

$x=-\dfrac{5}{2}+\dfrac{1}{3}$

$x=-\dfrac{13}{6}$

`Vậy` $x=-\dfrac{13}{6}$

$b)$ $\dfrac{1}{2}x+\dfrac{1}{5}=1$

$\dfrac{x}{2}+\dfrac{1}{5}=1$

$\dfrac{x}{2}+\dfrac{1}{5}-\dfrac{1}{5}=1-\dfrac{1}{5}$

$\dfrac{x}{2}=\dfrac{4}{5}$

$x=\dfrac{4}{5}\cdot 2$

$x=\dfrac{8}{5}$

`Vậy` $x=\dfrac{8}{5}$

$c)$ $\left|x-\frac{1}{4}\right|=1$

TH1: $x-\dfrac{1}{4}=-1$

$x=1+\dfrac{1}{4}$

$x=-\dfrac{3}{4}$

TH2: $\:x-\dfrac{1}{4}=1$

$x=1+\dfrac{1}{4}$

$x=\dfrac{5}{4}$

$\text{Vậy x $\in$ }$ $\left\{-\dfrac{3}{4};\dfrac{5}{4}\right\}$