diketahui la+bl=2√19, jika lal=4 dan lbl=6 maka la+bl adalah...

|a + b| = 2√19
|a + b|^2 = (2√19)^2
|a|^2 + 2ab + |b|^2 = 4(19)
4^2 + 2ab + 6^2 = 76
16 + 2ab + 36 = 76
2ab = 24

|a - b|^2 = |a|^2 - 2ab + |b|^2
|a - b|^2 = 4^2 - 24 + 6^2
|a - b|^2 = 28
|a - b| = √28 = 2√7

^ = pangkat