Cho \(\overrightarrow{a}=\left(2x;3\right),\overrightarrow{b}=\left(8;9\right),\overrightarrow{c}=\left(2+x;-3\right)\). Véc tơ \(\overrightarrow{b}=2\overrightarrow{a}-\overrightarrow{c}\) nếu:
\(x=\dfrac{10}{3}\) \(x=-\dfrac{10}{3}\) \(x=3\) \(x=2\) Hướng dẫn giải:\(\overrightarrow{b}=2\overrightarrow{a}-\overrightarrow{c}=2\left(2x;3\right)-\left(-2+x;-3\right)=\left(4x;6\right)-\left(2+x;-3\right)\) \(=\left(3x-2;9\right)\).
Suy ra \(3x-2=8\Leftrightarrow x=\dfrac{10}{3}\).
