Question

[Phan Khải Đăng]

giúp êm zới mấy  anh chị ui 

Answer 1

[Nguyễn Hoàng Minh]

Bài 1:

\(a,=\left(2\dfrac{3}{4}+\dfrac{1}{4}\right)+\left(\dfrac{4}{21}+\dfrac{17}{21}\right)-\dfrac{1}{2}=3+1-\dfrac{1}{2}=\dfrac{3}{2}\\ b,=-\dfrac{2}{3}\left(43\dfrac{1}{4}-13\dfrac{1}{4}\right)=-\dfrac{2}{3}\cdot30=-20\\ c,=-\dfrac{11}{3}:\left(\dfrac{5}{2}\cdot\dfrac{3}{5}-\dfrac{10}{3}\right)=-\dfrac{11}{3}:\left(-\dfrac{8}{3}\right)=\dfrac{11}{8}\)

Bài 2:

\(a,\Rightarrow x+\dfrac{1}{3}=-\dfrac{1}{3}\Rightarrow x=-\dfrac{2}{3}\\ b,\Rightarrow\left|x+\dfrac{2}{5}\right|=1\dfrac{1}{2}+\dfrac{1}{2}=2\\ \Rightarrow\left[{}\begin{matrix}x=2-\dfrac{2}{5}=\dfrac{8}{5}\\x=-2-\dfrac{2}{5}=-\dfrac{12}{5}\end{matrix}\right.\\ c,\Rightarrow\left(x+\dfrac{1}{4}\right)^3=-\dfrac{27}{8}=\left(-\dfrac{3}{2}\right)^3\\ \Rightarrow x+\dfrac{1}{4}=-\dfrac{3}{2}\Rightarrow x=-\dfrac{7}{4}\)

Bài 3:

Gọi số máy 3 đội ll là a,b,c(máy;a,b,c∈N*)

Áp dụng tc dtsbn:

\(10a=8b=12c\Rightarrow\dfrac{10a}{120}=\dfrac{8b}{120}=\dfrac{12c}{120}\\ \Rightarrow\dfrac{a}{12}=\dfrac{b}{15}=\dfrac{c}{10}=\dfrac{b-a}{15-12}=\dfrac{3}{3}=1\\ \Rightarrow\left\{{}\begin{matrix}a=12\\b=15\\c=10\end{matrix}\right.\)

Vậy...

Bài 5:

\(\dfrac{a}{2}=\dfrac{b}{5}=\dfrac{c}{7}=\dfrac{a-b+c}{4}=\dfrac{a+2b-c}{5}\\ \Rightarrow A=\dfrac{4}{5}\)