Diketahui |a| = 10, |b| = 6, |a + b| = 14, maka |a – b| = ….
A.2√19
B.76
C.36
D.2√15
E.12
Jawab:
|a| = 10, |b| = 6, |a + b| = 14
|a – b| = …. ?
|a – b|2 = 2|a|2 + 2|b|2 – |a + b|2
= 2(10)2 + 2(6)2 – 142
= 200 + 72 – 196
|a – b|2 = 76
|a – b| = √76 = 2√19
Jawaban: A
