Ta có : \(\frac{x}{3}=\frac{y}{4}\Rightarrow\frac{x}{9}=\frac{y}{12}\left(1\right)\)

           \(\frac{y}{6}=\frac{z}{5}\Rightarrow\frac{y}{12}=\frac{z}{10}\left(2\right)\)

Từ (1) và (2) => \(\frac{x}{9}=\frac{y}{12}=\frac{z}{10}\)

Ta có : \(\frac{x}{9}=\frac{y}{12}=\frac{z}{10}=\frac{3x}{27}=\frac{2y}{24}=\frac{5z}{50}=\frac{3x-2y+5z}{27-24+50}=\frac{86}{53}\) (đề sai)

b) Đặt : k = \(\frac{x}{5}=\frac{y}{7}\)

=> k² \(=\frac{x}{5}.\frac{y}{7}=\frac{xy}{35}=\frac{140}{35}=4\)

=> k = -2;2

+ k = 2 thì \(\frac{x}{5}=2\Rightarrow x=10\)

                 \(\frac{z}{7}=2\Rightarrow z=14\)

+ k = -2 thì \(\frac{x}{5}=2\Rightarrow x=-10\)

                 \(\frac{z}{7}=2\Rightarrow z=-14\)

Vậy................................

\(a)\frac{1}{3}+\frac{-2}{5}+\frac{1}{6}+\frac{-1}{5}\le x< \frac{-3}{4}+\frac{2}{7}+\frac{-1}{4}+\frac{3}{5}+\frac{5}{7}\)

\(\Rightarrow\frac{1}{3}+\frac{1}{6}+\frac{-2}{5}+\frac{-1}{5}\le x< \frac{-3}{4}+\frac{-1}{4}+\frac{2}{7}+\frac{5}{7}+\frac{3}{5}\)

\(\Rightarrow\frac{2}{6}+\frac{1}{6}+\frac{-3}{5}\le x< -1+1+\frac{3}{5}\)

\(\Rightarrow\frac{1}{2}+\frac{-3}{5}\le x< \frac{3}{5}\)

\(\Rightarrow\frac{-1}{10}\le x< \frac{6}{10}\)

\(\Rightarrow-1\le x< 6\)

\(\Rightarrow x\in\left\{-1;0;1;2;3;4;5\right\}\)

Bài b tương tự

bạn ơi bạn giải câu b được ko. mk ko biết làm câu b

Biết rồi mà đi đố người khác . Chịu chị luôn em lạy 2 tay

tìm n   N để \(\frac{n}{n+1}\) + \(\frac{n}{n+2}\) là số tự nhiên

giúp mik với sắp thi r

a) \(\frac{-8}{3}+\frac{7}{5}+\frac{-71}{15}\)< \(x\) < \(\frac{-13}{7}+\frac{19}{14}+\frac{-7}{2}\)

Ta có: \(\frac{-8}{3}+\frac{7}{5}+\frac{-71}{15}\)

=\(\frac{-40}{15}+\frac{21}{15}+\frac{-71}{15}\)

=\(\frac{-90}{15}\)

=\(-6\)

Ta có: \(\frac{-13}{7}+\frac{19}{14}+\frac{-7}{2}\)

=\(\frac{-26}{14}+\frac{19}{14}+\frac{-49}{14}\)

=\(\frac{-56}{14}\)

=\(-4\)

=> \(-6\)< \(x\)<\(-4\)

=> \(x=-5\)

b)\(\frac{5}{17}+\frac{-4}{9}+\frac{-20}{31}+\frac{12}{17}+\frac{-11}{31}\)< \(\frac{x}{9}\)<\(\frac{-3}{7}+\frac{7}{15}+\frac{4}{-7}+\frac{8}{15}+\frac{2}{3}\)

Ta có: \(\frac{5}{17}+\frac{-4}{9}+\frac{-20}{31}+\frac{12}{17}+\frac{-11}{31}\)

=\(\left(\frac{5}{17}+\frac{12}{17}\right)+\left(\frac{-20}{31}+\frac{-11}{31}\right)+\frac{-4}{9}\)

=\(1+\left(-1\right)+\frac{-4}{9}\)

=\(0+\frac{-4}{9}\)

=\(\frac{-4}{9}\)

Ta có: \(\frac{-3}{7}+\frac{7}{15}+\frac{4}{-7}+\frac{8}{15}+\frac{2}{3}\)

=\(\frac{-3}{7}+\frac{7}{15}+\frac{-4}{7}+\frac{8}{15}+\frac{2}{3}\)

=\(\left(\frac{-3}{7}+\frac{-4}{7}\right)+\left(\frac{7}{15}+\frac{8}{15}\right)+\frac{2}{3}\)

=\(\left(-1\right)+1+\frac{2}{3}\)

=\(0+\frac{2}{3}\)

=\(\frac{2}{3}\)

=> \(\frac{-4}{9}\)< \(\frac{x}{9}\)<\(\frac{2}{3}\)

=

=> \(\frac{-4}{9}\)<\(\frac{x}{9}\)<\(\frac{6}{9}\)

=> \(-4\)< \(x\)<\(6\)

=>\(x\in\left\{-3;-2;-1;0;1;2;3;4;5\right\}\)

Bạn làm ra đi