` (x - 1)(x^{2} + 2) = 0 `
` => ` \(\left[ \begin{array}{l}x-1=0\\x^{2}+2=0\end{array} \right.\)
` => ` \(\left[ \begin{array}{l}x=1\\x^{2}=-2 (loại)\end{array} \right.\)
` => x = 1 `
` (x + 1) + (x + 3) + (x + 5) + ... + (x + 99) = 0 `
` => x + 1 + x + 3 + x + 5 + ... + x + 99 = 0 `
` => (x + x + x + ... + x) + (1 + 3 + 5 + ... + 99) = 0 `
` => 50x + [(1 + 99) + (3 + 97) + ... + (49 + 51)] = 0 `
` => 50x + [100 + 100 + ... + 100] = 0 `
` => 50x + [100 . 25] = 0 `
` => 50x + 2500 = 0 `
` => 50x = -2500 `
` => x = -50 `
