0,25 + \(\dfrac{3}{5}-\left(\dfrac{1}{8}-\dfrac{2}{5}+1\dfrac{1}{4}\right)\)

= 0,25 + \(\dfrac{3}{5}-\dfrac{39}{40}\)

= \(\dfrac{10}{40}+\dfrac{24}{40}-\dfrac{39}{40}\)

= \(\dfrac{10+24-39}{40}\)

= \(\dfrac{-5}{40}=\dfrac{-1}{8}\)

:)

Nếu a - b = c

Thì:

1. a - c = b 

2. c + b = a 

Thay x = \(\left\{2;3\right\}\) thành \(x\in\left\{2;3\right\}\) giùm mik

x - 20 khi x \(\ge\) 20 (không tính số âm)

\(\dfrac{1}{7}< \dfrac{x}{7}< \dfrac{4}{7}\)

<=> 1 < x < 4

<=> x = \(\left\{2;3\right\}\)

b. \(\dfrac{5}{3}+\left(-\dfrac{2}{7}\right)-\left(-1,2\right)\)

= \(\dfrac{35}{21}+\dfrac{-6}{21}+\dfrac{25,2}{21}\)

= \(\dfrac{35+\left(-6\right)+25,2}{21}\)

= \(\dfrac{54,2}{21}\)

cấm copy

Ối, ảo quá

Mik nhìn mãi ko ra, bn giỏi quá