Question

Tìm x:

\(\left(\dfrac{3x}{7}+1\right);\left(-4\right)=\dfrac{-1}{28}\)

Answer 1

\(\left(\dfrac{3x}{7}+1\right):\left(-4\right)=\dfrac{-1}{28}\)

\(\Leftrightarrow\dfrac{3x}{7}+1=\dfrac{-1}{28}.\left(-4\right)\)

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

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

\(\Leftrightarrow\dfrac{3x}{7}=\dfrac{-6}{7}\)

\(\Leftrightarrow3x=-6\)

\(\Leftrightarrow x=-2\)

Answer 2

Mình không viết lại đề nữa nhé! Dấu " ; " đổi thành dấu " : " (phép chia)\(\Leftrightarrow\dfrac{3x+7}{7}\cdot\left(-\dfrac{1}{4}\right)=-\dfrac{1}{28}\)

\(\Leftrightarrow\dfrac{-3x-7}{28}=-\dfrac{1}{28}\)

\(\Rightarrow-3x-7=-1\)

\(\Leftrightarrow3x=-6\)

\(\Leftrightarrow x=-2\)

Vậy x = -2

Answer 3

\(\left(\dfrac{3x}{7}+1\right):\left(-4\right)=\dfrac{-1}{28}\)

⇔ \(\left(\dfrac{3x}{7}+\dfrac{7}{7}\right):\dfrac{-4}{1}=\dfrac{-1}{28}\)

⇔ \(\dfrac{3x+7}{7}:\dfrac{-4}{1}=\dfrac{-1}{28}\)

⇔ \(\dfrac{3x+7}{7}.\dfrac{1}{-4}=\dfrac{-1}{28}\)

⇔ \(\dfrac{3x+7}{-28}=\dfrac{-1}{28}\)

⇔ 28.(3x + 7) = -1.(-28)

⇔ 84x + 196 = 28

⇔ 84x = 28 - 196

⇔ 84x = -168

⇔ x = -2

Answer 4

\(\left(\dfrac{3x}{7}+1\right):\left(-4\right)=\dfrac{-1}{28}\)

➞\(\dfrac{3x}{7}+1=\dfrac{-1}{28}.\left(-4\right)\)

➞\(\dfrac{3x}{7}+1=\dfrac{1}{7}\)

➞\(\dfrac{3x}{7}=\dfrac{1}{7}-1\)

➞\(\dfrac{3x}{7}=\dfrac{-6}{7}\)

➞3x= -6

➞x= -6:3

➞x=-2

    Vậy x=-2

Answer 5

Ta có: \(\left(\dfrac{3x}{7}+1\right):\left(-4\right)=\dfrac{-1}{28}\)

\(\Leftrightarrow\dfrac{3x}{7}+1=\dfrac{-1}{28}\cdot\left(-4\right)=\dfrac{1}{7}\)

\(\Leftrightarrow\dfrac{3x}{7}=\dfrac{-6}{7}\)

hay \(x=\dfrac{-6}{7}:\dfrac{3}{7}=\dfrac{-6}{7}\cdot\dfrac{7}{3}=-2\)

Vậy: S={-2}