Let a, b, c be three non-coplanar and mutually perpendicular vectors of the same magnitude K. If r is any vector satisfying the equation: a × ((r - b) × a) + b × ((r - c) × b) + c × ((r - a) × c) = 0, then r is equal to:

If a = (0, -1, 2), b = (1, 0, -1) and c = (2, -1, 0), then which of the following is a unit vector parallel to a - b - c?

If a = 2î + 3ȷ and b = î - ȷ, then a - b is:

If vectors a and b are perpendicular with |a| = 5 and |b| = 12, then |a + b| is equal to: