Toán Lớp 7: tính giá trị biểu thức A= $2x^{2}$ -3x+2021 tại x thỏa mãn |x-1|= $\frac{1}{2}$
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Toán Lớp 7: tính giá trị biểu thức A= $2x^{2}$ -3x+2021 tại x thỏa mãn |x-1|= $\frac{1}{2}$
Comments ( 1 )
A = 2021\\
A = 2020
\end{array} \right.\)
\left| {x – 1} \right| = \dfrac{1}{2}\\
\to \left[ \begin{array}{l}
x – 1 = \dfrac{1}{2}\\
x – 1 = – \dfrac{1}{2}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{3}{2}\\
x = \dfrac{1}{2}
\end{array} \right.\\
Thay:\left[ \begin{array}{l}
x = \dfrac{3}{2}\\
x = \dfrac{1}{2}
\end{array} \right.\\
\to \left[ \begin{array}{l}
A = 2.{\left( {\dfrac{3}{2}} \right)^2} – 3.\dfrac{3}{2} + 2021\\
A = 2.{\left( {\dfrac{1}{2}} \right)^2} – 3.\dfrac{1}{2} + 2021
\end{array} \right.\\
\to \left[ \begin{array}{l}
A = 2021\\
A = 2020
\end{array} \right.
\end{array}\)