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