Determinar em $\,\mathbb{R}\,$ o conjunto verdade das equações $\phantom{X}3x\,-\,\left[\,2\,-\,(x\,-\,1)\,\right]\,=\,5x\phantom{X}$
resposta:
$\,3x\,-\,\left[\,2\,-\,(x\,-\,1)\,\right]\,=\,5x\; \Leftrightarrow$ $\,3x\,-\,\left[\,2\,-\,x\,+\,1\right]\,=\,5x\;\Leftrightarrow$ $\,3x\,-\,2\,+\,x\,-\,1\,=\,5x\; \Leftrightarrow$ $\,3x\,+\,x\,-\,5x\,=\,2\,+\,1\;\Leftrightarrow$ $\,-x\,=\,3\;\Leftrightarrow\;x\,=\,-3\phantom{XX}$ V = {-3}×