a) Show that the set of vectors {u1 = <1 2 -1>, u2 = <-1 -1 0>, u3= <2 5 4>} spans R^3

b)Express the vector v = <1 3 -2> in terms of the spanning set in part a).

I already answered a), I just don't know how to answer b)

By expressing does that mean I should just include the vector v in the set of given vectors? I'm not really sure with this one. Please help me. thanks!