` e) ` ` |x + 3| . |x - 1| = 0 `
` => ` \(\left[ \begin{array}{l}x+3=0\\x-1=0\end{array} \right.\)
` => ` \(\left[ \begin{array}{l}x=-3\\x=1\end{array} \right.\)
` f) ` ` |x - 1| . (x^{2} + 1) = 0 `
Do: ` x^{2} ≥ 0 ` ` ∀ ` ` x ` ` ∈ ` ` R `
` <=> x^{2} + 1 ≥ 1 `
` => |x - 1| = 0 `
` => x - 1 = 0 `
` => x = 1 `