(20 poin) No 12 pakai cara (Jawaban terbaik langsung dipilih)

|a - b| = 1
|a - b|^2 = 1^2
|a|^2 - 2ab + |b|^2 = 1
√3^2 - 2ab + 1^2 = 1
3 - 2ab + 1 = 1
3 = 2ab

|a + b|^2 = |a|^2 + 2ab + |b|^2
|a + b|^2 = √3^2 + 3 + 1^2
|a + b|^2 = 3 + 3 + 1
|a + b| = √7

^ = pangkat