Question

Tính và tìm x:

a) \(\dfrac{-1}{4}\).13\(\dfrac{9}{11}\) - 0,25 . 6\(\dfrac{2}{11}\)

b) \(\dfrac{31}{9}\). /x/ - \(\dfrac{5}{2}\) = \(\dfrac{8}{3}\)

Answer 1

\(a)\dfrac{-1}{4}.13\dfrac{9}{11}-0,25.6\dfrac{2}{11}\)

\(=\dfrac{-1}{4}.\dfrac{152}{11}-\dfrac{1}{4}.\dfrac{68}{11}\)

\(=-38-\dfrac{17}{11}\)

\(=\dfrac{-418}{11}+\dfrac{-17}{11}\)

\(=\dfrac{-435}{11}\)

\(b)\dfrac{31}{9}.\left|x\right|-\dfrac{5}{2}=\dfrac{8}{3}\)

\(\Leftrightarrow\dfrac{31}{9}.\left|x\right|=\dfrac{16}{6}+\dfrac{15}{6}\)

\(\Leftrightarrow\dfrac{31}{9}.\left|x\right|=\dfrac{31}{6}\)

\(\Leftrightarrow\left|x\right|=\dfrac{31}{6}.\dfrac{9}{31}\)

\(\Leftrightarrow\left|x\right|=1,5\)

\(\Leftrightarrow x\in\left\{1,5;-1,5\right\}\)

Vậy \(x\in\left\{1,5;-1,5\right\}\)