Question

[FAIRY TAIL]

Tìm x ,biết

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

b,\(\dfrac{3}{2}-1+4x=\dfrac{2}{3}-7x\)

c,\(2.\left(\dfrac{3}{4}-5x\right)=\dfrac{4}{5}-3x\)

d, \(4.\left(\dfrac{1}{2}-x\right)-5.\left(x-\dfrac{3}{10}\right)=\dfrac{7}{4}\)

Answer 1

[Nguyễn Thanh Hằng]

a/ \(\dfrac{1}{3}-\dfrac{2}{5}+3x=\dfrac{3}{4}\)

\(\Leftrightarrow\dfrac{-1}{15}+3x=\dfrac{3}{4}\)

\(\Leftrightarrow3x=\dfrac{49}{60}\)

\(\Leftrightarrow x=\dfrac{49}{180}\)

Vậy....

b/ \(\dfrac{3}{2}-1+4x=\dfrac{2}{3}-7x\)

\(\Leftrightarrow\dfrac{1}{2}+4x=\dfrac{2}{3}-7x\)

\(\Leftrightarrow4x+7x=\dfrac{2}{3}-\dfrac{1}{2}\)

\(\Leftrightarrow11x=\dfrac{1}{6}\)

\(\Leftrightarrow x=\dfrac{1}{66}\)

Vậy....

c/ \(2\left(\dfrac{3}{4}-5x\right)=\dfrac{4}{5}-3x\)

\(\Leftrightarrow\dfrac{3}{2}-10x=\dfrac{4}{5}-3x\)

\(\Leftrightarrow-10x+3x=\dfrac{4}{5}-\dfrac{3}{2}\)

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

\(\Leftrightarrow x=-\dfrac{1}{10}\)

Vậy .....

Answer 2

[Nguyễn Thanh Hằng]

d/ \(4\left(\dfrac{1}{2}-x\right)-5\left(x-\dfrac{3}{10}\right)=\dfrac{7}{4}\)

\(\Leftrightarrow2-4x-5x-\dfrac{3}{2}=\dfrac{7}{4}\)

\(\Leftrightarrow2+\left(-4x\right)+\left(-5x\right)+\left(\dfrac{-3}{2}\right)=\dfrac{7}{4}\)

\(\Leftrightarrow-9x+\dfrac{1}{2}=\dfrac{7}{4}\)

\(\Leftrightarrow-9x=\dfrac{5}{4}\)

\(\Leftrightarrow x=-\dfrac{5}{36}\)