Question

bài 3 : tìm x , làm chi tiết 

a ) -2/5 + 4/5 . X = 3/5 

b ) 2/5 + 3/4 : X =  -1/2

Answer 1

a, \(x=\left(\dfrac{3}{5}+\dfrac{2}{5}\right):\dfrac{4}{5}=\dfrac{5}{4}\)

b, \(x=\left(-\dfrac{1}{2}-\dfrac{2}{5}\right).\dfrac{3}{4}=-\dfrac{27}{40}\)

Answer 2

a)\(x=\left(\dfrac{3}{5}+\dfrac{2}{5}\right):\dfrac{4}{5}=\dfrac{5}{4}\)

b)\(x=\left(-\dfrac{1}{2}-\dfrac{2}{5}\right)\times\dfrac{3}{4}=-\dfrac{27}{40}\)

Answer 3

5/4

- 27/40

Answer 4

\(a,-\dfrac{2}{5}+\dfrac{4}{5}x=\dfrac{3}{5}\)

\(\Leftrightarrow\dfrac{4}{5}x=\dfrac{3}{5}+\dfrac{2}{5}\)

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

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

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

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

\(b,\dfrac{2}{5}+\dfrac{3}{4}:x=-\dfrac{1}{2}\)

\(\Leftrightarrow\dfrac{3}{4}:x=-\dfrac{1}{2}-\dfrac{2}{5}\)

\(\Leftrightarrow\dfrac{3}{4}:x=-\dfrac{5}{10}-\dfrac{4}{10}\)

\(\Leftrightarrow\dfrac{3}{4}:x=-\dfrac{9}{10}\)

\(\Leftrightarrow x=\dfrac{3}{4}:\dfrac{-9}{10}\)

\(\Leftrightarrow x=\dfrac{3}{4}\times\dfrac{10}{-9}\)

\(\Leftrightarrow x=-\dfrac{5}{6}\)