Question

Tính giá trị biểu thức A=x\(^2\)-3x+1 khi |x+\(\dfrac{1}{3}\)|=\(\dfrac{2}{3}\)

Answer 1

\(\left|x+\dfrac{1}{3}\right|=\dfrac{2}{3}\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{3}=\dfrac{2}{3}\\x+\dfrac{1}{3}=-\dfrac{2}{3}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=-1\end{matrix}\right.\)

- Với \(x=\dfrac{1}{3}\Rightarrow A=\left(\dfrac{1}{3}\right)^2-3.\dfrac{1}{3}+1=\dfrac{1}{9}\)

- Với \(x=-1\Rightarrow A=\left(-1\right)^2-3\left(-1\right)+1=5\)