Question

tìm x biết

a) \(\dfrac{2}{7}\)x - \(\dfrac{1}{2}\) = \(\dfrac{3}{4}\) : \(\sqrt{\dfrac{49}{64}}\)

b) (3x +1 )⁶ = 81³

c) | x + 2016 | + | x + 2017 | + | x + 2018 | = 6x

Answer 1

a,\(\dfrac{2}{7}x-\dfrac{1}{2}=\dfrac{3}{4}:\sqrt{\dfrac{49}{64}}\)

\(\Leftrightarrow\dfrac{2}{7}x-\dfrac{1}{2}=\dfrac{6}{7}\)

\(\Leftrightarrow\dfrac{2}{7}x=\dfrac{19}{14}\)

\(\Leftrightarrow x=\dfrac{19}{4}\)

Answer 2

Với mọi \(x\in R\)

\(\left|x+2016\right|+\left|x+2017\right|+\left|x+2018\right|\ge0\Leftrightarrow6x\ge0\Leftrightarrow x\ge0\)

với \(x\ge0\) ta được: \(\left\{{}\begin{matrix}\left|x+2016\right|=x+2016\\\left|x+2017\right|=x+2017\\\left|x+2018\right|=x+2018\end{matrix}\right.\)

\(pt\Leftrightarrow3x+6051=6x\Leftrightarrow3x=6051\Leftrightarrow x=2017\)

Answer 3

b,\(\left(3x+1\right)^6=81^3\)

\(\Leftrightarrow\left(3x+1\right)^6=\left(9^2\right)^3\)

\(\Leftrightarrow3x+1=9\)

\(\Leftrightarrow3x=8\)

\(\Leftrightarrow x=\dfrac{8}{3}\)

Vậy...