Question

tìm x, biết:

a, 1\(\dfrac{2}{5}\)x+\(\dfrac{4}{5}\)=-\(\dfrac{7}{10}\)

b, 5-3x=2\(\dfrac{2}{7}\)

Answer 1

Giải:

a) \(1\dfrac{2}{5}x+\dfrac{4}{5}=-\dfrac{7}{10}\)

\(\Leftrightarrow\dfrac{7}{5}x+\dfrac{4}{5}=-\dfrac{7}{10}\)

\(\Leftrightarrow\dfrac{7}{5}x=-\dfrac{7}{10}-\dfrac{4}{5}\)

\(\Leftrightarrow\dfrac{7}{5}x=-\dfrac{3}{2}\)

\(\Leftrightarrow x=-\dfrac{3}{2}:\dfrac{7}{5}=-\dfrac{15}{14}\)

Vậy ...

b) \(5-3x=2\dfrac{2}{7}\)

\(\Leftrightarrow5-3x=\dfrac{16}{7}\)

\(\Leftrightarrow3x=5-\dfrac{16}{7}\)

\(\Leftrightarrow3x=\dfrac{19}{7}\)

\(\Leftrightarrow x=\dfrac{19}{7}:3=\dfrac{19}{21}\)

Vậy ...