Chapter 1, Problem 28E

If vector $\stackrel{\to }{u}$ is a linear combination of vectors $\stackrel{\to }{v}$ and $\stackrel{\to }{w}$ ,and $\stackrel{\to }{v}$ is a linear combination of vectors $\stackrel{\to }{p},\stackrel{\to }{q}$ , and $\stackrel{\to }{r}$ , then $\stackrel{\to }{u}$ must be a linear combination of $\stackrel{\to }{p},\stackrel{\to }{q},\stackrel{\to }{r}$ , and $\stackrel{\to }{w}$ .