Question

thực hiện phép tính: \(\left(x-\dfrac{1}{2}\right)^3\) = 81

Answer 1

\(\left(x-\dfrac{1}{2}\right)^3=81=\left(\sqrt[3]{81}\right)^3\)

\(\Leftrightarrow x-\dfrac{1}{2}=\sqrt[3]{81}\)

\(\Leftrightarrow x=\sqrt[3]{81}+\dfrac{1}{2}\)

 

Answer 2

`#3107.101107`

`(x - 1/2)^2 = 81?`

`=> (x - 1/2)^2 = (+-9)^2`

`=>`\(\left[{}\begin{matrix}x-\dfrac{1}{2}=9\\x-\dfrac{1}{2}=-9\end{matrix}\right.\)

`=>`\(\left[{}\begin{matrix}x=9+\dfrac{1}{2}\\x=-9+\dfrac{1}{2}\end{matrix}\right.\)

`=>`\(\left[{}\begin{matrix}x=\dfrac{19}{2}\\x=-\dfrac{17}{2}\end{matrix}\right.\)

Vậy, `x \in {-17/2; 19/2}.`