Question

[Nguyễn Xuân Mong]

Giúp mk nhé các bn học giỏi Toán ơi!!!

Answer 1

[Nguyễn Thanh Hằng]

Bài 1 :

\(a\)) \(\dfrac{4}{15}:-\dfrac{8}{5}+\left(-1\dfrac{5}{6}\right)\)

\(=\dfrac{4}{15}:\dfrac{-8}{5}+\dfrac{-11}{6}\)

\(=\dfrac{4}{15}.\dfrac{-5}{8}+\dfrac{-11}{6}\)

\(=\dfrac{-1}{6}+\dfrac{-11}{6}=-2\)

\(b\)) \(\dfrac{-8}{13}+\dfrac{-7}{12}-\dfrac{-19}{12}+\dfrac{-5}{13}+\dfrac{1}{2}\)

\(=\dfrac{-8}{13}+\dfrac{-7}{12}+\dfrac{19}{12}+\dfrac{-5}{13}+\dfrac{1}{2}\)

\(=\left(\dfrac{-8}{13}+\dfrac{-5}{13}\right)+\left(\dfrac{-7}{12}+\dfrac{19}{12}\right)+\dfrac{1}{2}\)

\(=\left(-1\right)+1+\dfrac{1}{2}\)

\(=0+\dfrac{1}{2}=\dfrac{1}{2}\)

Answer 2

[Nguyễn Thanh Hằng]

Bài 2 :

a) \(x+\dfrac{1}{3}=\dfrac{3}{7}\)

\(x=\dfrac{3}{7}-\dfrac{1}{3}\)

\(x=\dfrac{2}{21}\)

Vậy \(x=\dfrac{2}{21}\) là giá trị cần tìm

b) \(\dfrac{x}{5}-\dfrac{3}{5}=\dfrac{1}{5}\)

\(\dfrac{x}{5}=\dfrac{1}{5}+\dfrac{3}{5}\)

\(\dfrac{x}{5}=\dfrac{4}{5}\)

\(\Rightarrow x=4\)

Vậy \(x=4\) là giá trị cần tìm

c)\(\left|x-12\right|=15\Rightarrow\left[{}\begin{matrix}x-12=15\\x-12=-15\end{matrix}\right.\)

\(+\))\(x-12=15\)

\(x=15+12\)

\(x=27\)

+)\(x-12=-15\)

\(x=-15+12\)

\(x=-3\)

Vậy \(x\in\left\{27,-3\right\}\) là giá trị cần tìm