Let v1 = (2, 4, 1, 2), v2 = (1, 1, 1, 3), and v3 = (2, 1, 2, 1)
in R 4 .
1. Find a vector u2 in the span of v1 and v2 that's perpendicular
to v1.
2. Find a vector u3 in the span of v1, v2 and v3 that's
perpendicular to v1 and v2.
Explain why v1, u2, u3 are mutually perpendicular vectors with the
same span as v1, v2, v3. Find the closest vector in the span of v1,
v2, v3 to (2, 2, 1, 3).