<p>If the magnitude of vectors a and b are 5 and 12, respectively, then the magnitude of vector b-a could not be: 5</p>
<p>Why is 5 the answer? I have no idea how to do this question. Someone please explain!!</p>
<p>is that on Official Guide? the explanation is quite clear I think. Basically, vector a, vector b and vector b-a make a triangle. And we have triangle inequality which is:</p>
<p>magnitude of (b-a) > magnitude of b - magnitude of a = 12 - 5 = 7</p>
<p>so magnitude of (b-a) cant be 5</p>